Ruby & Sapphire (Corundum) Inclusions | The Lotus Gemology Crystal Registry

E. Billie Hughes and Richard W. Hughes
Corundum Inclusions • A Crystal Registry


Solid inclusions have been used by gemologists as a means of determining origin. While there is a great deal of overlap from one source to another, there are also important differences. For example, while apatite has been identified in sapphire from Madagascar, Myanmar and Sri Lanka, apatite has never been identified in sapphire from Kashmir. Thus the purpose of this article is to give a full listing of solid inclusions in gem corundums from around the world, with each occurrence fully referenced. This is provided with the goal of making origin determination of ruby and sapphire more accurate.

It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.
Sherlock Holmes, "A Scandal in Bohemia"

Inclusions in Ruby & Sapphire (Corundum)

Corundums may contain a rich variety of solid inclusions. These are often related to type of geologic process of formation. Thus a knowledge of basic geologic principles is useful in understanding the inclusion types.

Geology of Corundum Deposits

Gem quality ruby and sapphire deposits around the world are mainly of two types: metamorphic origin, where corundum occurs associated with marble. These include:

Metamorphic processes

  • Amphibolite: Australia (Hart's Range), Greenland, Kenya, Madagascar, Malawi, Mozambique, Tanzania (Longido, Winza)
  • Biotite: Madagascar (Sahambano)
  • Cordieritite: Madagascar (Iankaroka)
  • Gneiss: India (Mysore)
  • Granulite: Sri Lanka
  • Mafic-Ultramafic: Tanzania (Longido)
  • Marble: Afghanistan, China (Yunnan), Kenya (Pamreso), Macedonia (Prilep), Myanmar, Nepal, Pakistan, Tajikistan, Tanzania (Mahenge, Morogoro), Vietnam (Yen Bai, Quy Chau)
  • Migmatite: Tanzania (Morogoro)
  • Pegmatite: India (Kashmir): Pegmatite associated with actinolite-tremolite lenses
  • Kenya (Mangari), Tanzania (Umba): Desilicated pegmatites cutting or in contact with serpentinite
  • Skarn: Madagascar (Andranondambo)

In addition, there are alluvial gem corundum deposits thought to have formed via metamorphism where the nature of the original host rocks is unknown. These include:

  • Madagascar (Ilakaka area), Sri Lanka, Tanzania (Tunduru)

Magmatic processes

Corundums have also been found in magmatic rocks. These include:

  • Alkali basalts: Australia, Cambodia, Cameroon, China, Ethiopia, France, Kenya, Israel, Madagascar (north), New Zealand, Nigeria, Rwanda, Scotland, Thailand, Vietnam (Dak Nong)
  • Lamprophyre: Yogo Gulch, MT (USA)
  • Syenite: Kenya (Garba Tula)

There are also alluvial gem corundum deposits associated with magmatic processes where the nature of the original host rocks is unknown. These include:

  • USA: Dry Cottonwood, Missouri River, Rock Creek, MT

Ages of corundum-bearing rocks

Corundum bearing rocks generally fall into three broad categories, as follows:

Pan-African orogeny: 730–450 million years ago (Ma)

Deposits in East Africa, Madagascar, Sri Lanka and southern India generally formed 730–550 million years ago, associated with the Pan-African orogeny, where eastern and western Gondwana collided.

Himalayan orogeny: 45–5 Ma

The Himalayan orogenic event occurred 25–5 million years ago (Giuliani & Fallick et al., 2017), where the Indian subcontinent collided with and was subducted under the Asia plate, producing the greatest mountain chain on Earth.

Cenozoic alkali basalt extrusions: 65–1 Ma

Corundum is also associated with alkali basalts (65–1 million years ago). While forming deeper in the earth, corundum crystals were brought to the surface by basalt eruptions. These include:

  • Australia, Cambodia, Cameroon, China, France, Kenya, Israel, Madagascar (north), New Zealand, Nigeria, Rwanda, Thailand, Vietnam.

The oldest corundums have been found in Greenland, and are believed to be approx. 2.7 billion years old.

Inclusion Types

Primary cavities

Corundum often plays host to primary cavities (negative crystals). These are often filled with liquid and gaseous CO2, and may also contain solids such as diaspore and/or graphite. This combination is particularly common in corundums from Sri Lanka.

Secondary Cavities

Corndum contains a wide variety of secondary fluid inclusions. These are often filled with liquid and gaseous CO2.

Solids

Corundum is host to a rich variety of solids. These can be placed into the following categories according to a scheme first developed by Gübelin (1973):

  • Protogenetic: Solids that formed before the host
  • Syngenetic: Solids that formed simultaneously with the host
  • Epigenetic: Solids that formed after the host. These form through a process of exsolution.

Secondary (Exsolved) Solids

Exsolution is the “unmixing” of a solid solution. At high temperatures, crystals have more defects, and thus are better able to absorb impurities. As the crystal cools, defects are reduced. This may force impurities to crystallize out. But because of the constraints placed on their movement by the solid host, impurity atoms are unable to travel large distances. Therefore, rather than forming large crystals, they migrate short distances to form multitudes of tiny needles, plates and particles, along the directions in the host where space permits.

A number of exsolved minerals have been found in corundum. These include:

  • Boehmite
  • Diaspore
  • Gibbsite
  • Hematite
  • Ilmenite
  • Kaolinite
  • Rutile

Traces of these exsolved minerals often show up in the infrared spectra. Some of these minerals may also be present as epigenetic deposits in fissures.

Growth Features

Growth features can be divided into two broad categories, as follows:

  • Twinning
  • Growth zoning

Twinning

Twinning in corundum can occur at the time of growth. These are known as growth twins, when, as a crystal is growing, it begins growing in a new direction. These typically occur as single planes only, rather than being repeated throughout the crystal.

If certain types of crystals are subjected to mechanical stress or pressure at any time after their formation, the bonds between planes of atoms may be broken and the planes “slip” or “glide” across one another into a twinned position, with new bonds immediately formed (if the pressure is too great, however, the crystal just breaks). This type of twinning often occurs repeatedly throughout a crystal (and is termed ‘polysynthetic twinning’), and due to the pressure that produced it, such crystals often contain many cracks (as well as healed cracks). Examples: Rhombohedral twinning in corundum, quartz (amethyst) and calcite.

Growth Zoning

During a crystal’s growth, coloring agents may not be available in consistent amounts. The result is a layered appearance of lighter and darker lines (or bands) which follow the external surfaces of the crystal. This is similar to the growth rings of trees, except that with single crystals, the external surfaces are flat and meet at specific angles. Thus the growth lines of single crystals will always be straight (never curved, unless one looks in directions not parallel to the faces along which they formed). They may form parallel to any of the faces that are, or were, present while the crystal was growing.

Table 1: Solids in Ruby & Sapphire (Corundum)

Solid Inclusion Type Corundum Origin Earliest Reference

Aluminite Group – Monoclinic or Triclinic

  • Aluminite – Monoclinic – Al2(SO4)(OH)4 · 7H2O
  • USA (Rock Creek, MT: Zwaan & Buter et al., 2015)
 Zwaan & Buter et al., 2015
Amphibole Group (includes hornblende) – Monoclinic or Orthorhombic
  • Pargasite – Monoclinic – {Na}{Ca2}{Mg4Al}(Al2Si6O22)(OH)2

Pargasite

  • Greenland (pargasite; Thirangoon, K., 2009)
  • India (Kashmir; pargasite; Gübelin, 1973)
  • Mozambique (Montepuez: Pardieu and Sangsawang et al., 2013)
  • Myanmar (Mogok: Gübelin, 1973)
  • Tanzania (Winza: Peretti & Peretti et al., 2008)

General Amphibole

  • Afghanistan (Jegdalek: Barthoux, 1933)
  • Madagascar (Andranondambo: Schwarz & Petsch et al., 1996)
  • Malawi (Chimwadzulu Hill: hornblende; Henn & Bank, 1990)
  • Rwanda (Krzemnicki & Hänni et al., 1996)
  • Tanzania (Winza: Schwarz & Pardieu, et al., 2008)
  • Thailand (sapphire: Bo Ploi: Gunawardene & Chalwla, 1984)
 Barthoux, 1933
Anatase – Tetragonal – TiO2  – Polymorph of Akaogiite, Brookite, Rutile, TiO2 II, UM1991-08-O:Ti
  • USA (Rock Creek, MT: Zwaan & Buter et al., 2015)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011
 Khoi & Sutthirat et al., 2011
Andalusite – Orthorhombic – Al2(SiO4)O – Polymorph of Kyanite, Sillimanite
  • Madagascar (Ilakaka: Hughes, in press)
 Hughes (in press)
Anhydrite – Orthorhombic – CaSO4
  • Myanmar (Smith & Dunaigre, 2001)
  • Thailand (Bo Welu: Promwongnan & Sutthirat, 2019b)
  • USA (Dry Cottonwood, Rock Creek, MT: Zwaan & Buter et al., 2015)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)
 Smith & Dunaigre, 2001

Apatite Group – Hexagonal

Chlorapatite

  • No origin given (Schubnel, 1967)
  • Sri Lanka (Gübelin & Koivula, 2008)

Fluorapatite

  • Colombia  (Keller & Koivula et al., 1985)

General Apatite

  • Afghanistan (Jegdalek: Beesley, 1986)
  • Cambodia (Pailin: Hughes, unpublished)
  • Kenya (ruby: Mangari: Gübelin & Koivula, 2008)
  • Madagascar (ruby: Andilamena: Gübelin & Koivula, 2008); Andranondambo: Kiefert & Schmetzer et al., 2006; ruby: Vatomandry: Schwarz & Schmetzer, 2001)
  • Myanmar (Mogok: Gübelin & Koivula, 2008; Mong Hsu: Smith & Surdez, 1994)
  • Nigeria (Henn, 1986)
  • Pakistan (Hunza: Gübelin, 1982; Nangimali: Gübelin & Koivula, 2008)
  • Sri Lanka (Gübelin, 1969)
  • Tanzania (Morogoro: Hänni & Schmetzer, 1991; Tunduru: Chitty, 2009; Umba: Zwaan, 1974; Winza: Schwarz & Pardieu, et al., 2008)
  • Thailand/Cambodia (ruby: Gübelin, 1971)
  • USA (Dry Cottonwood, Rock Creek, MT: Zwaan & Buter et al., 2015)
  • Vietnam (Yen Bai; Kane & McClure et al., 1991)

Chlorapatite: Schubnel (1967)

Fluorapatite: Keller & Koivula et al., 1985

General: Gübelin, 1969

Aragonite Group – Orthorhombic
  • Myanmar (Mogok: ruby: Vertriest & Manorotkul et al., 2015)
 Vertriest, 2015

Baddeleyite Group – Monoclinic
  • Madagascar (Andranondambo: Gübelin & Koivula, 2008)
  • Madagascar? (Hughes, 2020, unpublished)
  • USA (unspecified, MT: Zwaan & Buter et al., 2015)

Guo et al., 1996

Gübelin & Peretti, 1997

Baryte (Barite) Group – Orthorhombic
  • USA (Rock Creek, MT: Zwaan & Buter et al., 2015)
 Zwaan & Buter et al., 2015
Böhmite (Boehmite) – Orthorhombic – AlO(OH) – Polymorph of Diaspore
  • Afghanistan (Jegdalek: Bowersox, 1985)
  • Greenland (Thirangoon, K., 2009)
  • Mozambique (Montepuez: Pardieu and Sangsawang et al., 2013)
  • Myanmar (sapphire: Atikarnsakul, U., Vertriest, W. et al., 2018)
  • Sri Lanka (Sahama & Lehtinen et al., 1973)
  • USA (Missouri River, MT: Zwaan & Buter et al., 2015)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)
 Sahama & Lehtinen et al., 1973
Brookite – Orthorhombic – TiO2 –  Polymorph of Akaogiite, Anatase, Riesite, Rutile, TiO2 II, UM1991-08-O:Ti
  • Myanmar (Mogok: Gübelin & Koivula, 1986)
 Gübelin & Koivula, 1986

Calcite Group – Hexagonal or Trigonal

 Calcite
  • Afghanistan (Jegdalek: Beesley, 1986)
  • India (Kashmir: Gübelin & Koivula, 2008)
  • Madagascar (Andranondambo: Kiefert & Schmetzer et al., 2006; Marosely: Cartier, 2009)
  • Myanmar (Mogok: Gübelin, 1973; Mong Hsu: Gübelin & Koivula, 2008)
  • Pakistan (Hunza: Gübelin, 1982; Nangimali: Gübelin & Koivula, 2008; Batakundi: Pardieu & Thirangoon et al., 2009)
  • Sri Lanka (Gübelin, 1953)
  • Tajikistan (Smith, 1998)
  • Tanzania (Tunduru: Chitty, 2009; Umba: Hänni, 1987)
  • USA (Dry Cottonwood, Missouri River, Yogo, MT: Gübelin & Koivula, 1986)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)

Magnesite

  • Greenland (Thirangoon, K., 2009)
  • Myanmar (Mogok: ruby: Vertriest, 2015)

Calcite: Gübelin, 1953

Magnesite: Thirangoon, K., 2009
Carbon – Amorphous – C
  • USA (Dry Cottonwood, MT: Zwaan & Buter et al., 2015)
 Zwaan & Buter et al., 2015
Catapleiite – Monoclinic – Na2Zr(Si3O9) · 2H2O – Polymorph of Gaidonnayite
  • Greenland (Thirangoon, K., 2009)
 Thirangoon, K., 2009

Chalcopyrite Group – Tetragonal
  • Mozambique (Montepuez: Pardieu and Sangsawang et al., 2013)
  • Sri Lanka (Gübelin, 1973)
  • Thailand/Cambodia (ruby: Gübelin, 1971)
  • USA (Rock Creek, MT: Zwaan & Buter et al., 2015)
 Gübelin, 1973

Chlorite Group – Mostly monoclinic (also triclinic or orthorhombic) – A5-6T4Z18

Clinochlore – Mg5Al(AlSi3O10)(OH)8 – Monoclinic
  • Greenland (Thirangoon, K., 2009)
  • Mozambique (Montepuez: Hughes, Hyperion Database, 2020)
  • Myanmar (Mong Hsu: Peretti & Schmetzer et al., 1995)
  • Pakistan (Hunza: Gübelin, 1982)
  • Rwanda (Krzemnicki & Hänni et al., 1996)
  • Tanzania (Winza: Peretti & Peretti et al., 2008)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)

Gübelin, 1982

Clinochlore – Hughes, Hyperion Database, 2020

Columbite Group – Orthorhombic

 Columbite-(Fe)
  • Australia (NSW, QLD: Coenraads, 1992)
  • Cambodia (Pailin: Saeseaw & Sangsawong et al., 2017b)
  • China (Fujian, Hainan, Shandong: Guo & Reilly et al., 1996)
  • Thailand (Bo Welu: Promwongnan & Sutthirat, 2019b)
Tantalite–(Fe)
  • Madagascar (Andapa: Diep, 2015))
  • Nigeria (Pardieu & Sangsawong et al., 2014)
  • Thailand (Bo Ploi: Diep, 2015)
  • Vietnam (Dak Lak: Diep, 2015)

Tantalite–(Mn)

  • Laos (Huay Xai: Diep, 2015)

Niobite – Gübelin, 1973

Columbite – Guo & Reilly et al., 1996

Tantalite – Pardieu & Sangsawong et al., 2014
Cordierite (iolite) – Orthorhombic – (Mg,Fe)2Al3(AlSi5O18)
  • Greenland (Thirangoon, K., 2009)
  • Vietnam (Dak Nong, Diep, 2015)
 Thirangoon, 2009
Cosalite – Orthorhombic – Pb2Bi2S5
  • Greenland (Thirangoon, K., 2009)
 Thirangoon, K., 2009
Cristobalite – Tetragonal – SiO2 – Polymorph of Coesite, Keatite, Mogánite, Quartz, Seifertite, Stishovite, Tridymite
  • USA: Byproduct of heat treatment (Rock Creek, MT: Zwaan & Buter et al., 2015)
 Zwaan & Buter et al., 2015
Dawsonite – Orthorhombic – NaAlCO3(OH)2
  • Myanmar (Mong Hsu ruby, in fluid inclusions, Giuliani & Dubessy et al., 2018)
 Giuliani & Dubessy et al., 2018

Diaspore Group – Orthorhombic

Diaspore

  • Madagascar (Marosely: Cartier, 2009)
  • Myanmar
    Mong Hsu ruby: Smith, 1995;
    Mogok: ruby: Vertriest & Manorotkul et al., 2015
    Mogok sapphire: Atikarnsakul & Vertriest et al., 2018)
  • Sri Lanka (Gübelin & Koivula, 2008)

Goethite

  • Myanmar (Mogok sapphire: Soonthorntanikul & Vertriest et al., 2017

Diaspore – Smith, 1995

Goethite – Gübelin, 1992

Dolomite Group – Trigonal

Ankerite

  • Gübelin & Koivula, 1986

Dolomite

  • Afghanistan (Jegdalek: Brückl, 1937)
  • Greenland (Thirangoon, K., 2009)
  • Madagascar (Andranondambo: Milisenda & Henn, 1996)
  • Myanmar (Mogok, Mong Hsu: Gübelin & Koivula, 1986; Smith & Surdez, 1994)
  • Pakistan (Hunza: Gübelin, 1982)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)
 Brückl, 1937

Epidote Supergroup – Monoclinic – {A12+A22+M13+M23+M33+}(Si2O7)(SiO4)O(OH)

  • Clinozoisite  – {Ca2}{Al3}(Si2O7)(SiO4)O(OH)
  • Epidote – {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)

Allenite

  • India (Kashmir: Hänni, 1990)
  • Tajikistan (Sorokina & Litvinenko et al., 2015)
  • USA (Rock Creek, MT: Zwaan & Buter et al., 2015)

Clinozoisite

  • Myanmar (Mong Hsu: Gübelin & Koivula, 2008)
  • USA (Dry Cottonwood, MT: Gübelin & Koivula, 2008)

Epidote

  • Tanzania (Songea: Gübelin & Koivula, 2008)
  • USA (Rock Creek, MT: Gübelin & Koivula, 2008; Dry Cottonwood, Missouri River, Rock Creek, MT: Zwaan & Buter et al., 2015)

Allenite

  • Hänni, 1990

Clinozoisite

  • Gübelin & Koivula, 2008

Epidote

  • Gübelin & Koivula, 2008

Euxenite Group – Orthorhombic or Amorphous

  • Fersmite – Orthorhombic – (Ca,Ce,Na)(Nb,Ta,Ti)2(O,OH,F)6
  • China (Mingxi, Fujian: Guo & O’Reilly et al., 1996)
 Guo & O’Reilly et al., 1996
Feldspar Group – Monoclinic or Triclinic
  • Andesine – Triclinic – (Na,Ca)[Al(Si,Al)Si2O8]
  • Anorthite – Triclinic – Ca(Al2Si2O8)
  • Albite – Triclinic – Na(AlSi3O8)
  • Bytownite – Triclinic – (Ca,Na)[Al(Al,Si)Si2O8]
  • Labradorite – Triclinic – (Ca,Na)[Al(Al,Si)Si2O8]
  • Microcline – Triclinic – K(AlSi3O8)
  • Orthoclase – Monoclinic – K(AlSi3O8)
  • Australia (Gübelin, 1969; Schubnel, 1972; Coldham, 1985; Coenraads, 1992)
  • Brazil (Diep, 2015)
  • Cambodia (Pailin: Gübelin, 1973)
  • China (Fujian, Jiangsu, Shandong: Guo & Reilly et al., 1996)
  • Colombia (Plagioclase: Duroc-Danner, 2002)
  • Greenland (Thirangoon, K., 2009)
  • India (Kashmir, plagioclase: Hänni, 1990a)
  • Laos (Huay Xai: Diep, 2015)
  • Madagascar (Andranondambo: Gübelin & Koivula, 2008; Marosely: Cartier, 2009)
  • Malawi (Anorthite, Chimwadzulu Hill: Henn & Bank, 1990)
  • Myanmar
    Mogok, ruby: Vertriest & Manorotkul et al., 2015
    Mong Hsu: Plagioclase; Peretti & Mullis et al., 1996)
  • Nigeria (Albite: Kiefert & Schmetzer, 1987)
  • Russia (Diep, 2015)
  • Tajikistan (Microcline & Plagioclase: Sorokina & Litvinenko et al., 2015)
  • Tanzania (Tunduru: Chitty, 2009; Umba: Gübelin & Koivula, 2008)
  • Thailand/Cambodia (ruby: Gübelin, 1971)
  • Thailand (sapphire: Bo Ploi: Gunawardene & Chalwla, 1984; Plagioclase: Chanthaburi: Saeseaw & Sangsawong et al., 2017a; Alkali & Plagioclase: Bo Welu: Promwongnan & Sutthirat, 2019b)
  • USA (Andesine, bytownite, labradorite, orthoclase, plagioclase, unspecified: Dry Cottonwood, Rock Creek, MT: Zwaan & Buter et al., 2015)
  • Vietnam (Plagioclase: Yen Bai; Khoi & Sutthirat et al., 2011; Quy Chau, Dak Nong, Dak Lak: Diep, 2015)
 Gübelin, 1969

Feldspathoid Group – Tetragonal, Hexagonal, Trigonal, Triclinic
  • Myanmar (Mogok sapphire: Atikarnsakul & Vertriest et al., 2018)
  • Thailand (Bo Ploi: Saminpanya & Sutherland, 2011; Bo Welu: Promwongnan & Sutthirat, 2019b)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)
 Saminpanya & Sutherland, 2011
Fergusonite – Tetragonal – YNbO4
  • Myanmar (Mogok; Gübelin, 1973)
 Gübelin, 1973

Fluorite Group – Isometric
  • Madagascar (Andranondambo: Gübelin & Koivula, 2008)
  • Myanmar (Mong Hsu: Peretti & Schmetzer et al., 1995)
  • Tanzania (Tunduru: Chitty, 2009)
 Peretti & Schmetzer et al., 1995
Garnet Group – Isometric – X3Z2(SiO4)3

Almandine

  • USA (Dry Cottonwood, Missouri River, Rock Creek, Yogo, MT: Zwaan & Buter et al., 2015)

Pyrope

  • Tanzania (Morogoro: Hänni & Schmetzer, 1991)
  • Thailand (ruby; Bo Rai, Bo Welu: Promwongnan, & Sutthirat, 2019a,b)
General Garnet
  • Afghanistan (Jegdalek: Brückl, 1937)
  • Myanmar (Mogok; Gübelin, 1953; Vertriest & Manorotkul et al., 2015)
  • Sri Lanka (Gübelin, 1948)
  • Tanzania (Winza: Schwarz & Pardieu, et al., 2008)
  • Thailand/Cambodia (in ruby: Gübelin, 1971)
 Brückl, 1937; Gübelin, 1948; Du Toit & Charoensrithanakul et al., 1995
Gibbsite – Monoclinic – Al(OH)3 – Polymorph of Bayerite, Doyleite, Nordstrandite, UM1990-28-OHF:Al
  • Myanmar (Mogok sapphire: Soonthorntanikul & Vertriest et al., 2017)
  • USA (Rock Creek, MT: Zwaan & Buter et al., 2015)
 Zwaan & Buter et al., 2015
Glass – Amorphous
  • USA (Yogo, MT: Gübelin & Koivula, 1986)
 Gübelin & Koivula, 1986
Grandidierite – Orthorhombic – (Mg,Fe2+)(Al,Fe3+)3(SiO4)(BO3)O2
  • Madagascar (Hain & Hughes, 2019)
 Hain & Hughes, 2019
Graphite – Hexagonal – C – Polomorph of Chaoite, Diamond, Lonsdaleite
  • Afghanistan (Jegdalek: Brückl, 1937)
  • Myanmar (Mogok: Kammerling & Scarratt et al., 1994)
  • Pakistan (Batakundi: Pardieu & Thirangoon et al., 2009)
  • Sri Lanka (Gübelin & Koivula, 1986)
  • Tanzania (Umba: Zwaan, 1974)
  • USA (Rock Creek, MT: Zwaan & Buter et al., 2015)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011; Dak Nong: Diep, 2015)
 Brückl, 1937

Halite Group – Isometric
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)
 Khoi & Sutthirat, C. et al., 2011

Hematite Group – Trigonal

Corundum

  • Greenland (Thirangoon, K., 2009)
  • Myanmar (Mogok; Gübelin, 1953)
  • Sri Lanka (corundum: Gübelin, 1940b)

Eskolaite

  • Synthetic ruby (Zhou, 2017)

Hematite

  • Afghanistan (Jegdalek: Barthoux, 1933)
  • India (Kashmir; Bui & Fritsch et al., 2013)
  • Madagascar (Andranondambo: (Schwarz & Petsch et al., 1996)
  • Rwanda (exsolved: Krzemnicki & Hänni et al., 1996)
  • Sri Lanka (Gübelin, 1953)
  • Tanzania (Umba: Hänni, 1987)
  • USA (Rock Creek, MT: Zwaan & Buter et al., 2015)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011; Dak Lak, Dak Nong: Diep, 2015)

Hematite – Barthoux, 1933

Corundum – Gübelin, 1940b

Eskolaite – Zhou, 2017

Humite Group – Orthorhombic or Monoclinic

  • Humite – Orthorhombic – (Mg,Fe2+)7(SiO4)3(F,OH)2
  • Chondrodite – Monoclinic – (Mg,Fe2+)5(SiO4)2(F,OH)2
  • Afghanistan (Jegdalek: Barthoux, 1933)
 Barthoux, 1933
Huntite – Trigonal – CaMg3(CO3)4
  • Myanmar (Mogok: ruby: Vertriest, 2015)
 Vertriest & Manorotkul et al., 2015

Ilmenite Group – Trigonal
  • Australia (Moon & Phillips, 1984)
  • India (star ruby: Karnataka: Panjikar & Panjikar, 2016)
  • Laos (Huay Xai: Diep, 2015)
  • Madagascar (Andapa: Diep, 2015)
  • Myanmar (Mogok sapphire: Soonthorntanikul & Vertriest et al., 2017)
  • Rwanda (Krzemnicki & Hänni et al., 1996)
  • Sri Lanka (Gunawardene & Rupasinghe, 1986)
  • Thailand (Bo Ploi: Diep, 2015)
  • USA (Dry Cottonwood, Rock Creek, MT: Zwaan & Buter et al., 2015)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011; Dak Lak: Diep, 2015)
 Moon & Phillips, 1984

Kaolinite-Serpentine Group – Hexagonal, Trigonal, Orthorhombic, Monoclinic, Triclinic

  • Kaolinite – Triclinic – Al2(Si2O5)(OH)4
  • Thailand: Ruby, Chanthaburi/Trat, epigenetic deposits in fissures (Sangsawong & Vertriest et al., 2017)
 Sangsawong & Vertriest et al., 2017
Kyanite – Triclinic – Al2(SiO4)O – Polymorph of Andalusite, Sillimanite
  • Mozambique (Montepuez: Pardieu and Sangsawang et al., 2013)
 Pardieu & Sangsawong et al., 2013

Marcasite Group – Orthorhombic
  • Afghanistan (Jegdalek: Bowersox & Foord et al., 2000)
  • Myanmar (Mogok: ruby: Vertriest & Manorotkul et al., 2015)
 Bowersox & Foord et al., 2000
Mica Group – Monoclinic

Biotite

  • India (Kashmir: Gübelin & Koivula, 2008)
  • Madagascar (Andranondambo: (Schwarz & Petsch et al., 1996; Gübelin & Koivula, 2008)
  • Myanmar (Mogok: ruby: Vertriest & Manorotkul et al., 2015)
  • Sri Lanka (Gübelin, 1973)
  • USA (Dry Cottonwood, Rock Creek, Yogo, MT: Gübelin & Koivula, 1986; Zwaan & Buter et al., 2015)

Margarite

  • Greenland (Thirangoon, K., 2009)
  • Mozambique (Montepuez: Pardieu and Sangsawang et al., 2013)
  • Tajikistan (Sorokina & Litvinenko et al., 2015)

Muscovite

  • Kenya (Mangari: Hunstiger, 1989–90; Key & Ochieng, 1991)
  • Madagascar (ruby: Ambosary: Gübelin & Koivula, 2008)
  • Myanmar (Mogok: Gübelin, 1953); Fuchsite: Mong Hsu: Peretti & Schmetzer et al., 1995)
  • Sri Lanka (Gübelin, 1940b)
  • Tajikistan: Fuchsite (Sorokina & Litvinenko et al., 2015)
  • Tanzania (Tunduru: Chitty, 2009)
  • Thailand (Bo Ploi: Diep, 2015)
  • USA (Dry Cottonwood, Rock Creek, Yogo, MT: Zwaan & Buter et al., 2015)
  • Vietnam (Yen Bai, Quy Chau: Diep, 2015)

Phlogopite

  • Greenland (Thirangoon, K., 2009)
  • Kenya (Mangari: Hunstiger, 1989–90; Key & Ochieng, 1991)
  • Madagascar (Andranondambo: Schwarz & Petsch et al., 1996; Gübelin & Koivula, 2008)
  • Myanmar (Mogok: ruby: Vertriest & Manorotkul et al., 2015)
  • Pakistan (Hunza: Gübelin, 1982)
  • Sri Lanka (Gübelin, 1973; Gübelin & Koivula, 1986)
  • Tanzania (Tunduru: Chitty, 2009)
  • Vietnam (various: Yen Bai, Quy Chau; Kane & McClure et al., 1991)

Trilithionite

  • USA (MT): Zwaan & Buter et al., 2015)

General Mica

  • Australia (Coldham, 1985)
  • India (star ruby: Karnataka: Panjikar & Panjikar, 2016)
  • Madagascar (Marosely: Cartier, 2009)
  • Mozambique (Montepuez: Pardieu and Sangsawang et al., 2013)
  • Rwanda (Krzemnicki & Hänni et al., 1996)
  • Thailand (Chanthaburi: Saeseaw & Sangsawong et al., 2017a)
 Gübelin, 1940b, 1982

Molybdenite Group – 
  • Thailand (Chanthaburi: Saeseaw & Sangsawong et al., 2017a)
 Saeseaw & Sangsawong et al., 2017

Monazite Group – Monoclinic

 Cheralite
  • Rwanda (Cheralite-(Ce): Krzemnicki & Hänni et al., 1996)
Monazite
  • Cambodia (Pailin: Saeseaw & Sangsawong et al., 2017b)
  • Madagascar (Ilakaka: Gübelin & Koivula, 2008)
  • Myanmar (Mogok: Gübelin, 1973)
  • Tanzania (Songea: Gübelin & Koivula, 2008; Tunduru: Chitty, 2009; Umba: Hänni, 1987)
  • Thailand (Bo Welu: Promwongnan & Sutthirat, 2019b)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)
 Gübelin, 1973
Nahcolite – Monoclinic – NaHCO3
  • USA (Rock Creek, MT: Zwaan & Buter et al., 2015)
 Zwaan & Buter et al., 2015
Nordstrandite – Triclinic – Al(OH)3 – Polymorph of Bayerite, Doyleite, Gibbsite, UM1990-28-OHF:Al
  • Vietnam (Yen Bai: Kane & McClure et al., 1991)
 Kane & McClure et al., 1991

Olivine Group – Orthorhombic – Fe22+SiO4 to Mg2SiO4
  • Myanmar (Mogok: Gübelin, 1973)
  • Thailand/Cambodia (ruby: Gübelin, 1971)
 Gübelin, 1971

Pentlandite Group – Isometric or Tetragonal
  • Australia (Coenraads, 1992)
 Coenraads, 1992

Pyrite Group – Isometric
  • Afghanistan (Jegdalek) (Barthoux, 1933)
  • Kenya (ruby: Mangari: Gübelin & Koivula, 2008)
  • Madagascar (ruby: Vatomandry: Gübelin & Koivula, 2008)
  • Myanmar (Mogok: Gübelin & Koivula, 2008)
  • Pakistan (Hunza: Gübelin, 1982; Nangimali: Gübelin & Koivula, 2008)
  • Sri Lanka (Gübelin, 1953)
  • Tanzania
    Songea: Johnson & Koivula et al., 1999
    Winza: Peretti & Peretti et al., 2008
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)
  • USA (Yogo, MT: Gübelin & Koivula, 1986)
 Barthoux, 1933

Pyrochlore Supergroup – Isometric – A2-mD2X6-wZ1-n (betafite; discredited)
  • Australia (Gübelin & Koivula, 1986)
  • Cambodia (Pailin: Gübelin, 1969)
  • Madagascar (Johnson & Koivula, 1997)
  • Nigeria (Kiefert & Schmetzer, 1987)
  • Thailand (Chanthaburi: Saeseaw & Sangsawong et al., 2017a)
  • USA (unspecified, MT: Zwaan & Buter et al., 2015)
  • Vietnam (sapphire: Lam Dong: Gübelin & Koivula, 2008)
 Gübelin, 1969
Pyroxene Group – Orthorhombic or Monoclinic – ABSi2O6

  • Augite – Monoclinic – (CaxMgyFez)(Mgy1Fez1)Si2O6

    • Fassaite – Monoclinic – (Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6]
  • Diopside – Monoclinic – CaMgSi2O6
  • Hedenbergite – Monoclinic – CaFe2+Si2O6

Augite (including Fassaite)

  • Myanmar (ruby; Mogok: Gübelin, 1973)

Diopside

  • Thailand/Cambodia (ruby: Gübelin, 1971)
  • USA (unspecified, MT; Gübelin & Koivula, 2008)
Hedenbergite
  • Madagascar (Andranondambo: Schwarz & Petsch et al., 1996)

General Pyroxene

  • Greenland (Thirangoon, K., 2009)
  • Rwanda (Krzemnicki & Hänni et al., 1996)
 Gübelin, 1971

Pyrrhotite Group – Hexagonal, Monoclinic or Triclinic
  • Afghanistan (Jegdalek: Bowersox & Foord et al., 2000)
  • Australia (Coenraads, 1992)
  • Madagascar (ruby: Vatomandry: Gübelin & Koivula, 2008)
  • Myanmar (ruby & sapphire: Mogok: Gübelin & Koivula, 1986)
  • Pakistan (Hunza: Gübelin, 1982)
  • Sri Lanka (Gübelin, 1969)
  • Tanzania (Umba: Zwaan, 1974; ruby: Songea: Gübelin & Koivula, 2008)
  • Thailand/Cambodia (ruby: Gübelin, 1971)
  • Thailand (sapphire: Bo Ploi: Gunawardene & Chalwla, 1984)
  • USA (Dry Cottonwood, MT: Gübelin & Koivula, 2008)
  • Vietnam (Yen Bai, Quy Chau: Kane & McClure et al., 1991)
 Gübelin, 1971
Quartz – Trigonal – SiO2
  • Thailand (Bo Welu: Promwongnan & Sutthirat, 2019b)
 Promwongnan & Sutthirat, 2019b

Rhabdophane Group – Hexagonal
  • Australia (Kings Plains, NSW: Guo & O’Reilly et al., 1996)
 Guo & O’Reilly et al., 1996

Rutile Group – Tetragonal
  • Afghanistan (Jegdalek: Barthoux, 1933)
  • Australia (Coenraads, 1992)
  • Colombia  (Keller & Koivula et al., 1985)
  • Greenland (Thirangoon, K., 2009)
  • Kenya (Mangari: Key & Ochieng, 1991)
  • Madagascar (ruby: Ambosary, Andilamena: Gübelin & Koivula, 2008); Andranondambo; Schwarz & Petsch et al., 1996; ruby: Vatomandry: Schwarz & Schmetzer, 2001)
  • Malawi (Chimwadzulu Hill: Hughes & Manorotkul et al., 2017)
  • Myanmar
    Mogok: Gübelin, 1953;
    Mong Hsu: J. Koivula, pers. comm., 28 Feb. 1995; Peretti & Mullis et al., 1996
  • Pakistan (Hunza: Gübelin, 1982)
  • Rwanda (Krzemnicki & Hänni et al., 1996)
  • Sri Lanka (Gübelin, 1940b)
  • Tajikistan (Henn & Bank et al., 1990)
  • Tanzania (Songea; Johnson & Koivula et al., 1999; rutile silk: Tunduru: Chitty, 2009)
  • USA (Rock Creek, Dry Cottonwood, Missouri River, Yogo, MT: Dunn, 1976; Zwaan & Buter et al., 2015)
  • Vietnam (Yen Bai/Quy Chau: Kane & McClure et al., 1991)
 Tschermak, 1878; Barthoux, 1933

Samarskite Group – Orthorhombic or Monoclinic
  • Australia (Anakie, QLD: Guo & O’Reilly et al., 1996)
 Guo & O’Reilly, 1996

Sapphirine Group – Monoclinic or Triclinic

  • Sapphirine – Monoclinic – Mg4(Mg3Al9)O4[Si3Al9O36]
  • Greenland (Thirangoon, K., 2009)
  • Thailand/Cambodia (ruby: Koivula & Fryer, 1987)
 Koivula & Fryer, 1987

Scapolite Group – Tetragonal – Na4Al3Si9O24Cl to Ca4Al6Si6O24CO3
  • Myanmar (Mogok; Kammerling & Scarratt et al., 1994)
 Kammerling & Scarratt et al., 1994
Sillimanite – Orthorhombic – Al2(SiO4)O5 – Polymorph of Andalusite, Kyanite

 

  • East Africa (Schneider & Smith, 2018)
  • Greenland (Thirangoon, K., 2009)
  • Madagascar (Marosely: Cartier, 2009)
  • Thailand (ruby, Bo Rai, Bo Welu:  Promwongnan, & Sutthirat, 2019a,b)
 Thirangoon, K., 2009

Smectite Group – Monoclinic
  • Tanzania (Umba: Zwaan, 1974)
 Zwaan, 1974

Sodalite Group – Isometric or Orthorhombic

  • Lazurite – Isometric – Na6Ca2(Al6Si6O24)(SO4,S,S2,S3,Cl,OH)2
  • Myanmar (Nanyazeik: Renfro & Pardieu, 2012)
 Renfro & Pardieu, 2012

Sphalerite Group – Isometric
  • Myanmar (Mogok: Gübelin, 1973)
  • USA (Dry Cottonwood, MT: Zwaan & Buter et al., 2015)
 Gübelin, 1973
Spinel Supergroup – Isometric
 Chromite
  • Mozambique (Montepuez: Pardieu and Sangsawang et al., 2013)

Gahnite (including Gahnospinel)

  • Australia (Coenraads, 1992)

Hercynite

  • Australia (Coenraads, 1992)
  • Rwanda (Hercynite/Gahnite: Krzemnicki & Hänni et al., 1996)
  • USA (Missouri River, Rock Creek, MT:  Garland, 2002)

Magnetite

  • Australia (Coenraads, 1992)
  • USA (Missouri River, Rock Creek, Yogo, MT:  Zwaan & Buter et al., 2015)
  • Vietnam (Dak Nong: Diep, 2015)

Spinel

  • Thailand (ruby, Bo Rai, Bo Welu: ruby: Promwongnan, & Sutthirat, 2019a,b)

General Spinel Group

  • Afghanistan (Jegdalek: Brückl, 1937)
  • China (Fujian, Jiangsu: Guo & Reilly et al., 1996)
  • India (Kashmir: Bui & Fritsch et al., 2013)
  • India (star ruby: Karnataka: Panjikar & Panjikar, 2016)
  • Madagascar (Andranondambo: (Kiefert & Schmetzer et al., 2006)
  • Myanmar (Mogok: Gübelin, 1953)
  • Pakistan (Hunza: Gübelin, 1982)
  • Sri Lanka (Gübelin & Koivula, 1986)
  • Tanzania (Morogoro: Hänni & Schmetzer, 1991; Umba: Zwaan, 1974; Winza: Schwarz & Pardieu, et al., 2008)
  • Thailand (sapphire: Bo Ploi: Co-rich, surrounded by glass rim; Jingfeng Guo & Griffen et al., 1994)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)
 Brückl, 1937

Staurolite Group – Monoclinic
  • Madagascar (Hughes, E.B., 2019)
 Hughes, E.B., 2019

Sulfur (Sulphur) Group – Orthorhombic or Monoclinic
  • Myanmar (Mogok: Fritsch & Rossman, 1990)
 Fritsch & Rossman, 1990
Tialite – Al2TiO5
  • India (star ruby: Karnataka: Panjikar & Panjikar, 2016)
 Panjikar & Panjikar, 2016

Titanite Group – Monoclinic or Triclinic
  • Afghanistan (Jegdalek: Barthoux, 1933)
  • Myanmar (Mogok: Gübelin, 1969)
  • Tajikistan (Smith, 1998)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)
 Barthoux, 1933
Topaz – Orthorhombic – Al2(SiO4)(F,OH)2
  • USA (Rock Creek, MT:  Zwaan & Buter et al., 2015)
 Zwaan & Buter et al., 2015
Tourmaline Group – Trigonal – Complex borosilicates
  • India (Kashmir: Mallet, 1882)
  • Myanmar (tourmaline on ruby, Mogok: Vertriest & Khowpong, 2017)
  • Pakistan (Batakundi: Hughes, E.B., 2019, Lotus Gemology Hyperion Database)
  • Tajikistan (Palke & Saeseaw et al., 2019)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011)
 Gübelin, 1973

Uraninite Group – Isometric

Thorianite

  • Madagascar (Andranondambo; Gübelin & Koivula, 2008)
Uraninite
  • Australia (Kings Plains, NSW; Guo & O’Reilly et al., 1996)
  • India (Kashmir; Hänni, 1990a)
  • Madagascar (ruby: Ilakaka, Gübelin & Koivula, 2008)
  • Sri Lanka (Gübelin, 1973)
  • USA (unspecified, MT:  Zwaan & Buter et al., 2015)

Uraninite: Gübelin, 1973

Thorianite: Gübelin & Koivula, 2008

Vesuvianite Group – Tetragonal

  • Vesuvianite – (Ca,Na,☐)19(Al,Mg,Fe3+)13(☐,B,Al,Fe3+)5(Si2O7)4(SiO4)10(OH,F,O)10
  • Myanmar (ruby: Renfro & Koivula, 2017)
 Renfro & Koivula, 2017

Wollastonite Group – Triclinic
  • Madagascar (Andranondambo: (Gübelin & Koivula, 2008)
 Gübelin & Koivula, 2008

Xenotime Group – Tetragonal
  • Madagascar (ruby: Ambosary: Gübelin & Koivula, 2008)
  • Sri Lanka (Gübelin & Koivula, 2008)
  • Tanzania (Tunduru: Chitty, 2009; Winza: Peretti, A., Peretti, F. et al., 2008)
 Gübelin & Koivula, 2008

Zeolite Group – All systems possible

  • Analcime – Triclinic – Na(AlSi2O6) · H2O
  • USA (Missouri River, Rock Creek, Yogo, MT: Gübelin & Koivula, 1986)
 Gübelin & Koivula, 1986

Zircon Group – Tetragonal

  • Thorite – Tetragonal – Th(SiO4)
  • Zircon – Tetragonal – Zr(SiO4)
 Thorite
  • Australia (Coenraads, 1992)
  • Cambodia (Gübelin, 1973)
  • Sri Lanka (Carbonin & Sbrignadello et al., 1998)
Zircon
  • Afghanistan (Jegdalek: Bowersox & Foord et al., 2000)
  • Australia (zircon: Gübelin & Koivula, 1986)
  • Cambodia (Saeseaw & Sangsawong et al., 2017)
  • China (Shandong: Diep, 2015)
  • India (Kashmir: Phukan, 1966)
  • India (star ruby: Karnataka: Panjikar & Panjikar, 2016)
  • Kenya (sapphire: Lodwar: Gübelin & Koivula, 2008)
  • Laos (Huay Xai: Diep, 2015)
  • Madagascar
    Ambosary, ruby: (Gübelin & Koivula, 2008);
    Andapa: (Diep, 2015); 
    Andranondambo: (Gübelin & Koivula, 2008)
    Ilakaka: (Wang & Scarratt et al., 2006)
    Marosely: (Cartier, 2009); 
    North: (Johnson & Koivula, 1997); 
    Vatomandry, ruby: (Schwarz & Schmetzer, 2001)
  • Malawi (Chimwadzulu Hill; Henn & Bank, 1990)
  • Myanmar (Mogok; Gübelin, 1950)
  • Nigeria (Henn, 1986)
  • Pakistan (Batakundi: Pardieu & Thirangoon et al., 2009)
  • Rwanda (Krzemnicki & Hänni et al., 1996)
  • Sri Lanka (zircon: Gübelin, 1940b)
  • Tajikistan (Smith, 1998)
  • Tanzania
    Morogoro: Hänni & Schmetzer, 1991;
    Songea: Gübelin & Koivula, 2008; 
    Tunduru: Chitty, 2009; 
    Umba: Zwaan, 1974)
  • Thailand (Bo Welu: Promwongnan & Sutthirat, 2019b)
  • USA (Dry Cottonwood, Missouri River, Rock Creek, Yogo, MT: Gübelin & Koivula, 1986; Zwaan & Buter et al., 2015)
  • Vietnam (Yen Bai: Khoi & Sutthirat et al., 2011; Dak Nong: Diep, 2015)

Zircon: Gübelin, 1940b

Thorite: Gübelin, 1973
Zirconolite – Orthorhombic – CaZrTi2O7
  • Tanzania (Winza: Peretti, A., Peretti, F. et al., 2008)
 Peretti, A., Peretti, F. et al., 2008
Zirkelite – Isometric – (Ti,Ca,Zr)O2-x
  • Madagascar (Andranondambo: Gübelin & Koivula, 2008)
 Gübelin & Koivula, 2008
Zoisite – Orthorhombic – Ca2Al3[Si2O7][SiO4]O(OH) – Dimorph of Clinozoisite
  • Mozambique (Montepuez: Hughes, Hyperion Database, 2020)
  • USA (Rock Creek, MT: Zwaan & Buter et al., 2015)
 Zwaan & Buter et al., 2015

 

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References & further reading

  • Atikarnsakul, U., Vertriest, W. et al. (2018) Characterization of blue sapphires from the Mogok Stone Tract, Mandalay region, Burma (Myanmar). Gemological Institute of America, Bangkok, June, 56 pp.; RWHL*.
  • Barthoux, J. (1933) Lapis-lazuli et rubis balais des cipolins afghans. Comptes Rendus de l’Academie des Sciences de France, Vol. 196, 10 April, pp.  1131–1134; RWHL.
  • Beesley, C.R. (1986) Pakistan’s emeralds: A trickle becomes a stream. Jewelers’ Circular-Keystone, February, pp. 359–365; RWHL.
  • Bowersox, G.W. (1985) A status report on gemstones from Afghanistan. Gems & Gemology, Vol. 21, No. 4, Winter, pp. 192–204; RWHL*.
  • Bowersox, G.W., Foord, E.E., Laurs, B.L., Shigley, J.E. and Smith, C.P. (2000) Ruby and sapphire from Jegdalek, Afghanistan. Gems & Gemology, Vol. 36, No. 2, Summer, pp. 110–126; RWHL*.
  • Brückl, K. (1937) Die Minerallagerstätten von Östafghanistan. Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, B-Bd 72, Abt. A, H 1, pp. 1–97; RWHL*.
  • Bui, H.N., Fritsch, E. et al. (2013) Kashmir sapphires: Geographical origin determination of top-quality blue sapphires versus science. International Gemmological Conference Proceedings, Hanoi, Vietnam, pp. 59–60; RWHL*.
  • Carbonin, S., Sbrignadello, G. et al. (1998) An interdisciplinary approach to identify­ing solid inclusions in corundum: thorite in a ‘Sri Lanka’ sapphire. Journal of Gemmology, Vol. 26, No. 4, October, pp. 262–264; RWHL.
  • Cartier, L. (2009) Ruby and sapphire from Marosely, Madagascar. Journal of Gemmology, Vol. 31, No. 5–8, pp. 171–179; RWHL.
  • Chitty, W. (2009) A Study of Sapphires and Rubies from Tanzania’s Tunduru District. Kingston University, London, BSc Thesis in Gemology and Applied Mineralogy, 32 pp.; RWHL*.
  • Coenraads, R.R. (1992) Sapphires and rubies associated with volcanic provinces: Inclusions and surface features shed light on their origin. Australian Gemmologist, Vol. 18, No. 3, pp. 70–78; RWHL*.
  • Coldham, T.S. (1985) Sapphires from Australia. Gems & Gemology, Vol. 21, No. 3, Fall, pp. 130–146; RWHL*.
  • Diep, P.T.M. (2015) Internal characteristics, chemical compounds and spectroscopy of sapphire as single crystals. Mainz University doctorate thesis; 140 pp.; RWHL*.
  • Du Toit, G., Charoensrithanakul, S. et  al. (1995) Lab Report: Cat’s eye blue sapphire; synthetic ruby crystal; irradiated orange star sapphire. JewelSiam, Vol. 6, No. 5, Oct–Nov, pp. 62–63; RWHL.
  • Dunn, P.J. (1976) Gem Notes: Inclusions in sapphires from Yogo Gulch, Montana. Gems & Gemology, Vol. 15, No. 7, Fall, p. 200; RWHL.
  • Duroc-Danner, J.M. (2002) A Study of Colombian Corundum. Université de Nantes, Nantes, Diplôme d’Université de Gemmologie, 217 pp.; RWHL*.
  • Emmett, J.L., Scarratt, K., McClure, S.F., Moses, T., Douthit, T.R., Hughes, R., Novak, S., Shigley, J.E., Wang, W., Bordelon, O. and Kane, R.E. (2003) Beryllium diffusion of ruby and sapphire. Gems & Gemology, Vol. 39, No. 2, Summer, pp. 84–135; RWHL*.
  • Fritsch, E. and Rossman, G.P. (1990) New technologies of the 1980s: Their impact in gemology. Gems & Gemology, Vol. 26, No. 1, Spring, pp. 64–75; RWHL.
  • Garland, M.I. (2002) The Alluvial Sapphire Deposits of Western Montana. University of Toronto, Canada, PhD thesis, 562 pp.; RWHL*.
  • Giuliani, G., Dubessy, J. et al. (2018) Fluid inclusion study of trapiche and non-trapiche rubies from the Mong Hsu district, Myanmar. Canadian Mineralogist, Vol. 56, No. 5, pp. 691–703; RWHL.
  • Gübelin, E.J. (1940a) Differences between Burma and Siam rubies. Gems & Gemology, Vol. 3, No. 5, Spring, pp. 69–72; RWHL*.
  • Gübelin, E.J. (1940b) Characteristics of Ceylon rubies. Gems & Gemology, Vol. 3, No. 8, pp. 121–124; RWHL.
  • Gübelin, E.J. (1942–43) Local peculiarities of sapphires. Gems & Gemology, Vol. 4, No. 3, Fall, pp. 34–39; No. 4, Winter, pp. 50–54; No. 5, Spring, pp. 66–69; RWHL.
  • Gübelin, E.J. (1948) Gemstone inclusions. Journal of Gemmology, Vol. 2, No. 7, July, pp. 7–39; RWHL*.
  • Gübelin, E.J. (1950) The diagnostic importance of inclusions in gemstones. Journal of Gemmology, Vol. 2, No. 7, July, pp. 281–303; RWHL*.
  • Gübelin, E.J. (1953) Inclusions as a Means of Gemstone Identification. Los Angeles, GIA, 220 pp.; RWHL*.
  • Gübelin, E.J. (1957) A contribution to the genealogy of inclusions. Journal of Gemmology, Vol. 6, No. 1, January, pp. 1–47; RWHL*.
  • Gübelin, E.J. (1968) Die Edelsteine der Insel Ceylon. Lucerne, privately published, 152 pp.; RWHL*.
  • Gübelin, E.J. (1969) On the nature of mineral inclusions in gemstones. Journal of Gemmology, Vol. 11, No. 5, Jan., pp. 149–192; RWHL*.
  • Gübelin, E.J. (1971) New analytical results of the inclusions in Siam rubies. Journal of Gemmology, Vol. 12, No. 7, July, pp. 242–252; RWHL*.
  • Gübelin, E.J. (1973) Internal World of Gemstones. Zürich, ABC Verlag, reprinted 1983, 234 pp.; RWHL*.
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About the authors

E. Billie Hughes visited her first gem mine (in Thailand) at age two and by age four had visited three major sapphire localities in Montana. A 2011 graduate of UCLA, she qualified as a Fellow of the Gemmological Association of Great Britain (FGA) in 2013. An award winning photographer and photomicrographer, she has won prizes in the Nikon Small World and Gem-A competitions, among others. Her writing and images have been featured in books, magazines, and online by Forbes, Vogue, National Geographic, and more. In 2019 the Accredited Gemologists Association awarded her their Gemological Research Grant. Billie is a sought-after lecturer and has spoken around the world to groups including Cartier and Van Cleef & Arpels. In 2020 Van Cleef & Arpels’ L’École School of Jewellery Arts staged exhibitions of her photomicrographs in Paris and Hong Kong.


Richard W. Hughes is one of the world’s foremost experts on ruby and sapphire. The author of several books and over 170 articles, his writings and photographs have appeared in a diverse range of publications, and he has received numerous industry awards. Co-winner of the 2004 Edward J. Gübelin Most Valuable Article Award from Gems & Gemology magazine, the following year he was awarded a Richard T. Liddicoat Journalism Award from the American Gem Society. In 2010, he received the Antonio C. Bonanno Award for Excellence in Gemology from the Accredited Gemologists Association. The Association Française de Gemmologie (AFG) in 2013 named Richard as one of the Fifty most important figures that have shaped the history of gems since antiquity. In 2016, Richard was awarded a visiting professorship at Shanghai's Tongji University. 2017 saw the publication of Richard and his wife and daughter's Ruby & Sapphire • A Gemologist's Guide, arguably the most complete book ever published on a single gem species and the culmination of nearly four decades of work in gemology. In 2018, Richard was named Photographer of the Year by the Gem-A, recognizing his photo of a jade-trading market in China, while in 2020, he was elected to the board of directors of the Accredited Gemologists Association and was appointed to the editorial review board of Gems & Gemology and The Australian Gemmologist magazine. Richard's latest book, Jade • A Gemologist's Guide, was published in 2022.

Notes

First published in ???