For those who wish to explore the literature of inclusions in gemstones further, we have selected the following articles and books that are of particular merit. Most of these are cited in the Lotus Gemology Hyperion Inclusion Database, but are listed below in a more convenient summary format. Many of the links will allow you to download a PDF copy of the original article.

You go from form… into the formless… into the void…
It is eternally quiet… it is eternally quiet… it never was…
Richard Alpert, Be Here Now

Literature on inclusions in gemstones

Monographs on inclusions in gems

• Chikayama, A. (1973) [Gem Identification By The Inclusion]. Tokyo, Japan, Gemmological Association of All Japan, in Japanese, 246 pp.; RWHL.
• Goutiere, A., de (1996) Wonders Within Gemstones: The Elusive Beauty of Gemstone Inclusions. Chicago, Gemworld International, 135 pp.; RWHL*.
• Goutiere, A., de (2014) Wonders Within Gemstones II. Friesen Press, 72 pp.; RWHL.
• Gübelin, E.J. (1953) Inclusions as a Means of Gemstone Identification. Los Angeles, GIA, 220 pp.; RWHL*.
• Gübelin, E.J. (1973) Internal World of Gemstones. Zürich, ABC Verlag, reprinted 1983, 234 pp.; RWHL*.
• Gübelin, E.J. and Koivula, J.I. (1986) Photoatlas of Inclusions in Gemstones. Zürich, Switzerland, ABC Edition, revised Jan., 1992; German edition, 1986 (Bildatlas der Einschlüsse Edelsteinen), 532 pp.; RWHL*.
• Gübelin, E.J. and Koivula, J.I. (2005) Photoatlas of Inclusions in Gemstones, Volume 2. Basel, Switzerland, Opinio Publishers, 830 pp.; RWHL*. Vol. 2 for spinel
• Gübelin, E.J. and Koivula, J.I. (2008) Photoatlas of Inclusions in Gemstones, Volume 3. Basel, Switzerland, Opinio Publishers, 672 pp.; RWHL*. Vol. 3 for corundum
• Hyršl, J. and Niedermayr, G. (2003) Geheimnisvolle Welt: Einschlüsse im Quarz—Magic World: Inclusions in Quartz. [In German and English], Haltern: Bode, 240 pp.; not seen.
• Lai Tai-An (1995) Gemstone Inclusions Identification. Taipei, Gemological Institute of Lai Tai-An, 343 pp.; RWHL*.
• Leeder, O., Thomas, R. and Klemm, W. (1987) Einschlüsse in Mineralen. Leipzig, VEB Deutscher Verlag für Grundstoffindustrie, 180 pp.; RWHL.
• Roedder, E. (1972) Composition of fluid inclusions. US Geological Survey Professional Paper, No. 440JJ, 164 pp.; RWHL* 
• Roedder, E. (1984) Fluid Inclusions. Reviews in Mineralogy, Washington, DC, Mineralogical Society of America, Reviews in Mineralogy: Vol. 12, 646 pp.; RWHL*.
• Samson, L., Anderson, A. et al. (2003) Fluid Inclusions: Analysis and Interpretation. Ottawa, Canada, Mineralogical Association of Canada, Short Course Series Volume 32, 374 pp.; RWHL.
• Smith, F.G. (1953) Historical Development of Inclusion Thermometry. Toronto, Univ. of Toronto Press, 149 pp.; RWHL.

A selection of monographs on inclusions in gems and minerals in the library of Lotus Gemology's Richard W. Hughes.

Inclusion photomicrography techniques

• Boehm, E. (2014) Photomicrography using a smartphone camera. Journal of Gemmology, Vol. 34, No. 1, pp. 6–7, RWHL.
• Gübelin, E.J. (1957) Application of phase contrast microscopy in gemmology. Journal of Gemmology, Vol. 6, No. 4, October, pp. 151–165; RWHL.
• Koivula, J.I. (1981) Photographing inclusions. Gems & Gemology, Vol. 17, No. 3, Fall, pp. 132–142, RWHL*.
• Koivula, J.I. (1982) Shadowing: A new method of image enhancement for gemological microscopy. Gems & Gemology, Vol. 18, No. 3, Fall, pp. 160–164; RWHL*.
• Koivula, J.I. (1982) Inclusions in a better light. Gemological Institute of America, Eash, D.M., ed., In International Gemological Symposium Proceedings, Santa Monica, CA, pp. 471–476; RWHL*.
• Koivula, J.I. (1982) Pinpoint illumination: a controllable system of lighting for gem microscopy. Gems & Gemology, Vol. 18, No. 2, pp. 83–86; RWHL.
• Koivula, J.I. (1984) The first-order red compensator: an effective gemological tool. Gems & Gemology, Vol. 20, No. 2, pp. 101–105; RWHL.
• Koivula, J.I. (2003) Photomicrography for gemologists. Gems & Gemology, Vol. 39, No. 1, Spring, pp. 4–23; RWHL*.
• Koivula, J.I. (2007) Photographing gems. In Focus, No. 7, September, pp. 24–59; RWHL**.
• Koivula, J.I. and Hughes, R.W. (2005) Living in the Dark Ages: The fiber-optic light. Lotusgemology.com; RWHL.
• Prince, N. (2014) Use of stacking software for expanding depth-of-field in inclusion photomicrography. Journal of Gemmology, Vol. 34 No. 3, pp. 188–189, RWHL.
• Overton, T.W. (2010) Gem News International: Smartphone photomicrography. Gems & Gemology, Vol. 46, No. 4, Winter, pp. 325–326, RWHL.
• Renfro, N. (2015) Digital photomicrography for gemologists. Gems & Gemology,Vol. 51, No. 2, Summer, pp. 144–159; RWHL*.
• Renfro, N. and Sanchez, D.J. (2015) G&G Microworld: Modified Rheinberg illumination. Gems & Gemology, Vol. 51, No. 3, Fall, pp. 328–329; RWHL.

The world's foremost authority on inclusions in gemstones, John Koivula, with his advanced Nikon SMZ25 stereoscopic microscope with built-in image stacking capability at the Gemological Institute of America's Carlsbad, CA laboratory. Image stacking is commonly used today to increase the depth-of-field for a medium that has extreme limits due to the high magnification. While such a photomicrographic system costs more than US$25,000, exceptional results can still be obtained with systems costing far less. Like all photography, the most important element is the person behind the lens and their vision to show us something in a way we've never seen it before. What separates experts from amateurs is not the equipment they use, but the manner in which they use it. John Koivula can produce superb photomicrographs from even a primitive system because he is an artist and can paint in a variety of mediums of various resolutlions. This is what separates fine art from idle scribbling. John Koivula is a master artist, and also a master scientist. This rare combination of sensitivtiy to both art and science have made John's work transcend each genre, expanding the interest in these tiny windows on the birth of our planet and life itself. Photo: Kevin Schumacher, GIA. Click on the image for a larger view.

Historical articles on inclusions in gems and crystals

• Brewster, D. (1826) On the existence of two new fluids in the cavities of minerals, which are immiscible, and possess remarkable physical properties. Transactions of the Royal Society of Edinburgh, Vol. 10, Part 1, pp. 1–41, 2 plates; RWHL.
• Brewster, D. (1827) Notice respecting the existence of the new fluid in a large cavity in a specimen of sapphire. Edinburgh Journal of Science, Vol. 6, pp. 155–156; RWHL.
• Davy, H. (1822) On the state of water and aeriform matter in cavities found in certain crystals. Philosophical Transactions of the Royal Society of London, Vol. 112, pp. 367–376; RWHL.
• Judd, J.W. (1895) On the structure-planes of corundum. Mineralogical Magazine, No. 11, pp. 49–55; RWHL*.
• Lea, I. (1869) Notes on microscopic crystals included in some minerals. Proceedings of the Academy of Natural Sciences of Philadelphia, Feb. 16, reprinted in Gems & Gemology, Fall, 1955, pp. 203–205; RWHL.
• Lea, I. (1869) Further notes on microscopic crystals. Proceedings of the Academy of Natural Sciences of Philadelphia, May 11, reprinted in Gems & Gemology, Fall, 1955, pp. 205–207, 218–219; RWHL.
• Lea, I. (1876) Notes on microscopic crystals included in some minerals. Proceedings of the Academy of Natural Sciences of Philadelphia, May, pp. 98–107 (reprinted in Gems & Gemology, Fall, 1955, pp. 230–236, 254); RWHL.
• Michel, H. (1926) Die künstlichen Edelsteine. Leipzig, Verlag von Wilhelm Diebener, 2nd edition, 477 pp.; RWHL*.
• Prinz, W. (1892) Les enclaves du saphir, du rubis, et du spinelle. Bulletin des séances de la Société belge de microscopie, Vol. 8, pp. 97–105, 1 pl.; RWHL*.
• Söchting, E. (1860) Die Einschlüsse von Mineralien in Krystallisirten Mineralien. Freiberg, Buchhandlung J.G. Engelhardt, 357 pp.; RWHL.
• Sorby, H.C. (1858) On the microscopical structure of crystals, indicating the origin of minerals and rocks. Quarterly Journal of the Geological Society of London, Vol. 14, pp. 453–500; RWHL.
• Sorby, H.C. and Butler, P.J. (1869) On the structure of rubies, sapphires, diamonds, and some other minerals. Proceedings of the Royal Society of London, Vol. 17, No. 109, pp. 291–302, 1 plate; RWHL.
• Tschermak, G. (1878) Optisches Verhalten von Korund-Krystallen [Optical behavior of corundum crystals]. Mineralogische und Petrographische Mittheilungen, Vol. 1, No. 4, pp. 362–364; RWHL*.

David Brewster was one of the first scientists to explore the internal world of crystals.

General references on the inclusions of ruby, sapphire and spinel

• Abduriyim, A. and Kitawaki, H. (2006) Applications of Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) to gemology. Gems & Gemology, Vol. 42, No. 2, Summer, pp. 98–118; RWHL*.
• Bowersox, G.W., Foord, E.E. et al. (2000) Ruby and sapphire from Jegdalek, Afghanistan. Gems & Gemology, Vol. 36, No. 2, Summer, pp. 110–126; RWHL*.
• Chauviré, B., Rondeau, B. et al. (2015) Blue spinel from the Luc Yen district of Vietnam. Gems & Gemology, Vol. 51, No. 1, Spring, pp. 2–17; RWHL.
• Crowningshield, R. and Nassau, K. (1981) The heat and diffusion treatment of natural and synthetic sapphires. Journal of Gemmology, Vol. 17, No. 8, Oct., pp. 528–541; RWHL*.
• Du Toit, G., Hughes, R.W. et al. (2006) Beryllium-treated blue sapphires. Bangkok, www.ruby-sapphire.com, RWHL.
• Du Toit, G., Thanachakaphad, J. et al. (2009) Beryllium treated blue sapphires: Continuing market observations and update including the emergence of larger size stones. Gemological Institute of America, 24 pp.; RWHL*.
• Emmett, J.L. (1999) Fluxes and the heat treatment of ruby and sapphire. Gems & Gemology, Vol. 35, No. 3, Fall, pp. 90–92; RWHL*.
• Emmett, J.L., Scarratt, K. et al. (2003) Beryllium diffusion of ruby and sapphire. Gems & Gemology, Vol. 39, No. 2, Summer, pp. 84–135; RWHL*.
• Eppler, W.F. (1959) The origin of healing fissures in gemstones. Journal of Gemmology, Vol. 7, No. 2, April, pp. 40–66; RWHL*.
• Eppler, W.F. (1964) Polysynthetic twinning in synthetic corundum. Gems & Gemology, Vol. 11, No. 6, Summer, pp. 169–175; RWHL*.
• Eppler, W.F. (1966) The origin of negative crystals in gemstones. Journal of Gemmology, Vol. 10, No. 2, April, pp. 49–56; RWHL*.
• Eppler, W.F. (1972) Needles in corundum other than rutile. Journal of Gemmology, Vol. 13, No. 2, pp. 41–44; RWHL*.
• Garnier, V., Ohnenstetter, D. et al. (2002) Rubis trapiches de Mong Hsu, Myanmar [Trapiche Rubies from Mong Hsu, Myanmar]. Revue de Gemmologie, a.f.g., No. 144, pp. 5–12; not seen.
• Gübelin, E.J. (1940) Differences between Burma and Siam rubies. Gems & Gemology, Vol. 3, No. 5, Spring, pp. 69–72; RWHL*.
• Gübelin, E.J. (1948) Gemstone inclusions. Journal of Gemmology, Vol. 1, 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*.
• Gunawardene, M. (1984) Reddish-brown sapphires from Umba Valley, Tanzania. Journal of Gemmology, Vol. 19, No. 2, April, pp. 139–144; RWHL.
• Guo, J., O’Reilly, S.Y. et al. (1996) Corundum from basaltic terrains: A mineral inclusion approach to the enigma. Contributions to Mineralogy and Petrology, Vol. 122, pp. 368–386; RWHL*.
• Guo, J., O’Reilly, S.Y. et al. (1996) Zircon inclusions in corundum megacrysts: I. Trace element geochemistry and clues to the origin of corundum megacrysts in alkali basalts. Geochemica et Cosmochimica Acta, Vol. 60, No. 13, pp. 2347–2363; RWHL.
• Hänni, H.A. (1987) On corundums from Umba Valley, Tanzania. Journal of Gemmology, Vol. 20, No. 5, January, pp. 278–284; RWHL*.
• Hänni, H.A. (1990) A contribution to the distinguishing characteristics of sapphire from Kashmir. Journal of Gemmology, Vol. 22, No. 2, pp. 67–75; RWHL*.
• Hänni, H.A., Schmetzer et al. (1994) Synthetic rubies by Douros: A new challenge for gemologists. Gems & Gemology, Vol. 30, No. 2, Summer, pp. 72–86; RWHL*.
• Hänni, H.A. (2001) Ruby heat treatment and fracture repair. Jewellery News Asia, No. 207, pp. 75–76; RWHL.
• Hughes, E.B., Koivula, J.I., Manorotkul, W., Renfro, N. and Hughes, R.W. (2019) Spinel inclusions: An exercise in aesthetics. InColor, No. 43, pp. 48–55.
• Hughes, R.W. (1984) Repaired surfaces found on rubies. Jewellery News Asia, No. 6, pp. 1, 33; RWHL*.
• Hughes, R.W. (1991) There's a rumble in the jungle: The sapphire face-lift face-off. Gemological Digest, Vol. 3, No. 2, pp. 17-31, RWHL*.
• Hughes, R.W. (1997) Ruby & Sapphire. Boulder, CO, RWH Publishing, 512 pp.; RWHL*.
• Hughes, R.W. and Galibert, O. (1998) Foreign affairs: Fracture healing/filling of Möng Hsu ruby. Australian Gemmologist, Vol. 20, No. 2, April–June, pp. 70–74; RWHL*.
• Hughes, R.W. (2002) The Skin Game: Orange sapphire treatment raises controversy. The Guide, Vol. 21, No. 2, Part 1, March–April, pp. 3–7; RWHL*.
• Hughes, R.W. and Emmett, J.L. (2004) Fluxed up: The fracture healing of ruby. The Guide, Vol. 23, Issue 5, Part 1, Sept.–Oct., pp. 1, 4–9; RWHL*.
• Hughes, R.W. and Emmett, J.L. (2005) Heat Seeker: UV fluorescence as a gemological tool. The Guide, Vol. 24, No. 5, Part 1, Sept.–Oct., pp. 1, 4–7; RWHL*.
• Hughes, R.W. and Koivula, J. (2005) Dangerous curves: Verneuil synthetic corundum. Bangkok, Lotus Gemology; RWHL.
• Hughes, R.W., Manorotkul, W. et al. (2014) Ruby & Sapphire: A Collector's Guide. Bangkok, Gem and Jewelry Institute of Thailand, 384 pp.; RWHL*.
• Hughes, R.W., Pardieu, V. et al. (2006) Moon over the Pamirs: Chasing ruby and spinel in Tajikistan. LotusGemology.com, RWHL*.
• Hughes, R.W., Manorotkul, W. et al. (2015) Let it bleed: New rubies from Madagascar. Bangkok, Lotus Gemology Co. Ltd., RWHL*.
• Johnson, M.L., Koivula, J.I. et al. (1999) Gem News: Rubies from Songea. Gems & Gemology, Vol. 35, No. 4, Winter, p. 215; RWHL.
• Kan-Nyunt, H.-P. (2013) Blue sapphires from the Baw Mar mine in Mogok. Gems & Gemology, Vol. 49, No. 4, Winter, pp. 223–232; RWHL*.
• Kane, R.E., Kammerling, R.C. et al. (1990) The identification of blue diffusion-treated sapphires. Gems & Gemology, Vol. 26, No. 2, Summer, pp. 115–133; RWHL*.
• Kane, R.E., McClure, S.F. et al. (1991) Rubies and fancy sapphires from Vietnam. Gems & Gemology, Vol. 27, No. 3, pp. 136–155; RWHL*.
• Kiefert, L. (2012) Gem News International: Unusual trapiche sapphire. Gems & Gemology, Vol. 48, No. 3, Fall, p. 229; RWHL.
• Koivula, J.I. (1980) “Thin films”: elusive beauty in the world of inclusions. Gems & Gemology, Vol. 16, No. 9, pp. 326–330; RWHL*.
• Koivula, J.I. (1980) Carbon dioxide as a fluid inclusion. Gems & Gemology, Vol. 16, No. 12, pp. 386–390; RWHL*.
• Koivula, J.I. (1983) Induced fingerprints. Gems & Gemology, Vol. 19, No. 4, pp. 220–227; RWHL*.
• Koivula, J.I. (1986) Carbon dioxide fluid inclusions as proof of natural-colored corundum. Gems & Gemology, Vol. 22, No. 3, pp. 152–155; RWHL*.
• Koivula, J.I. (1987) Internal diffusion. Journal of Gemmology, Vol. 20, No. 7/8, pp. 474–477; RWHL*.
• Koivula, J.I. (2009) Micro magma chambers in natural rubies and sapphires. Australian Gemmologist, Vol. 23, No. 11, July–September, pp. 509–512; RWHL*.
• Koivula, J.I. (2013) Useful visual clue indicating corundum heat treatment. Gems & Gemology, Vol. 49, No. 3, Fall, pp. 160–161; RWHL*.
• Koivula, J.I. and Hughes, R.W. (2005) Passport to obscurity: Testing yellow sapphire. Bangkok, LotusGemology.com, RWHL.
• Koivula, J.I. and Hughes, R.W. (2005) Following the Silk Road: Rutile in corundum. Bangkok, Lotusgemology.com, RWHL*.
• Leelawatanasuk, T., Atichat, W. et al. (2013) Cobalt-doped glass-filled sapphires: An update. Australian Gemmologist, Vol. 25, No. 1, Jan.–Mar., pp. 14–20; RWHL*.
• Lotus Gemology (2015) Lotus Gemology Lab Alert for Oiled Gems. Bangkok, LotusGemology.com, RWHL*.
• Müellenmeister, H.J. and Zang, J. (1995) Ein Trapiche-Rubin aus Myanmar (Burma) (A trapiche ruby from Myanmar). Lapis, Vol. 20, No. 12, p. 50; seen.
• Nassau, K. (1981) Heat treating ruby and sapphire: Technical aspects. Gems & Gemology, Vol. 17, No. 3, pp. 121–131; RWHL*.
• Pardieu, V., Thirangoon, K. et al. (2009) Sapphires reportedly from Batakundi/Basil area: A preliminary examination and a comparison with rubies and pink sapphires from other deposits in Central Asia. Gemological Institute of America, 12 May, 34 pp.; RWHL*.
• Pardieu, V., Sturman, N. et al. (2010) FAPFH/GFF treated ruby from Mozambique: A preliminary report. Gemological Institute of America, 11 May, 18 pp.; RWHL*.
• Pardieu, V., Sangsawong, S. et al. (2013) Rubies from the Montepuez area (Mozambique). Gemological Institute of America, October 5, 84 pp.; RWHL*.
• Pardieu, V. (2014) Hunting for "Jedi" spinels in Mogok. Gems & Gemology, Vol. 50, No. 1, Spring, pp. 46–57; RWHL.
• Pardieu, V., Sangsawong, S. et al. (2014) Blue sapphires from the Mambilla Plateau, Taraba State, Nigeria. Gemological Institute of America, 16 August, 47 pp.; RWHL*.
• Pardieu, V., Saeseaw, S. et al. (2015) "Low temperature" heat treatment of Mozambique ruby: Results report. Gemological Institute of America, 16 April, 34 pp.; RWHL*.
• Peretti, A. (1993) Foreign substances in Mong Hsu rubies. JewelSiam, Vol. 4, No. 5, p. 42; RWHL.
• Peretti, A., Schmetzer, K. et al. (1995) Rubies from Mong Hsu. Gems & Gemology, Vol. 31, No. 1, Spring, pp. 2–26; RWHL*.
• Peretti, A., Peretti, F. et al. (2008) Winza rubies identified. Contributions to Gemology, Vol. 7, pp. 1–97; RWHL*.
• Pisutha-Arnond, V., Promwongnan, S., Narudeesombat, N., Ounorn, P., Leelawatanasuk, T., Sripoonjan, T., Nilhud, N. and Atichat, W. (2019) Blue diffusion-treated natural & synthetic sapphires recently available in the market. Journal of the Gemmological Association of Hong Kong, Vol. 40, pp. 87–95; RWHL*.
• Roedder, E. (1962) Ancient fluids in crystals. Scientific American, Vol. 207, pp. 38–47; RWHL*.
• Roedder, E. (1982) Fluid inclusions in gems: Valuable defects. Gemological Institute of America, Eash, D.M., ed., In International Gemological Symposium Proceedings, Santa Monica, CA, pp. 479–502; RWHL*.
• Saeseaw, S., Wang, W. et al. (2009) Distinguishing Heated Spinels from Unheated Natural Spinels and from Synthetic Spinels. Gemological Institute of America, 13 pp.; RWHL.
• Saminpanya, S. (2001) Ti-Fe mineral inclusions in star sapphires from Thailand. Australian Gemmologist, Vol. 21, No. 3, pp. 125–128; RWHL.
• Scarratt, K. (1984) Notes from the laboratory [glass-filled sapphire]. Journal of Gemmology, Vol. 19, pp. 98–124; RWHL.
• Scarratt, K. (2009) A Discussion on Ruby‐Glass Composites & Their Potential Impact on the Nomenclature in use for Fracture‐Filled or Clarity Enhanced stones in General. Gemological Institute of America, 23 pp.; RWHL*.
• Schmetzer, K. and Schupp, F.-J. (1994) Flux-induced fingerprint patterns in synthetic ruby: An update. Gems & Gemology, Vol. 30, No. 1, Spring, pp. 33–38; RWHL.
• Schmetzer, K., Gübelin, E. et al. (2000) Oriented inclusions in spinels from Madagascar. Journal of Gemmology, Vol. 27, No. 4, pp. 229–232; RWHL.
• Schmetzer, K. (2000) Gem News: Spinel from Ilakaka, Madagascar. Gems & Gemology, Vol. 36, No. 2, Summer, pp. 169–170; RWHL.
• Schwarz, D., Pardieu, V. et al. (2008) Rubies and sapphires from Winza, central Tanzania. Gems & Gemology, Vol. 44, No. 4, Winter, pp. 322–347; RWHL*.
• Schwieger, R. (1990) Diagnostic features and heat treatment of Kashmir sapphires. Gems & Gemology, Vol. 26, No. 4, Winter, pp. 267–280; RWHL*.
• Smith, C.P. and Surdez, N. (1994) The Mong Hsu ruby: A new type of Burmese ruby. JewelSiam, Vol. 4, No. 6, Dec–Jan, pp. 82–98; RWHL.
• Sorokina, E.S., Litvinenko, A.K. et al. (2015) Rubies and Sapphires from Snezhnoe, Tajikistan. Gems & Gemology, Vol. 51, No. 2, pp. 160–175; RWHL.
• Sunagawa, I., Bernhardt, H.-J. et al. (1999) Texture formation and element partitioning in trapiche ruby. Journal of Crystal Growth, Vol. 206, pp. 322–330; RWHL.
• Sutherland, F.L., Coenraads, R.R. et al. (2015) Corundum (sapphire) and zircon relationships, Lava Plains gem fields, NE Australia: Integrated mineralogy, geochemistry, age determination, genesis and geographical typing. Mineralogical Magazine, Vol. 79, No. 3, pp. 545–581; RWHL.
• Thirangoon, K. (2009) Ruby and Pink Sapphire from Aappaluttoq, Greenland: Status of on‐going research. Gemological Institute of America, March, 18 pp.; RWHL.
• Wang, W., Scarratt, K. et al. (2006) The effects of heat treatment on zircon inclusions in Madagascar sapphires. Gems & Gemology, Vol. 42, No. 2, Summer, pp. 134–150; RWHL*.
• Zwaan, P.C. (1974) Garnet, corundum, and other gem minerals from Umba, Tanzania. Scripta Geologica, Vol. 20, pp. 19–30; RWHL*.

Key to references

• RWHL: References in the personal library of Lotus Gemology's Richard W. Hughes
• Seen: References not in the personal library of Lotus Gemology's Richard W. Hughes, but having been read by him
• Not seen: References not seen by Lotus Gemology's Richard W. Hughes
• * : References of particular merit

Acknowlegements

Lotus Gemology thanks organizations such as the GIA and Gem-A for their decades of publishing and especially for making many of their publications freely available for students and researchers. A special thanks to Elise Skalwold, who has helped us track down copies of many rare publications.