corundum, sapphire, India.12, Kashmir.12, inclusions.5, gems

Burma.12, corundum, ruby, sapphire, inclusions.5, gems

corundum, inclusions.5, gems

The geologist works like a detective in attempting to reconstruct the events of the remote past from the evidence of the present. Unlike the de­ tective, however, he works with events that occurred millions or even billions of years ago, and the clues he has to piece together are unusually meager. It is well known that most sedimentary rocks formed in sea water; it is less com­ monly recognized that most other geo­ logic processes in the apparently solid crust of the earth, including the forma­ tion of most ore deposits, have taken place in a bath of salty water. Droplets of these ancient mother liquors, pre­ served in the form of fluid inclusions" in many rocks and minerals, are clues to such processes. Although the droplets are minuscule, they enable the geolo­ gist to tell a number of things about the events of the past that would otherwise be completely hidden. These tiny sam­ ples of uids long since gone from the face of the earth have been known for almost 150 years, but they still conceal many secrets and merit much more in­ vestigation. Just about any crystal, natural or man­ made, that is grown from an aqueous solution will have uid inclusions. They are easily seen in a clear quartz crystal. Ordinarily the crystal will have a clear tip, but its base will show faint whitish streaks. A 10-power glass will generally resolve these streaks into innumerable separate liquid inclusions, each contain­ ing a tiny bubble. Most of them will look black, because light entering them is trapped by total re ection at the walls, hut a few may be at enough to transmit light clearly. The photomicrographs that illustrate this article were made by light transmitted through polished mineral plates and nearly perpendicular to the planes of somewhat attened inclusions. In size uid inclusions range from a diameter of probably less than one mi­ cron (a thousandth of a millimeter), below the limit of resolution of the light microscope, to a few centimeters. Inclu­ sions bigger than a millimeter in diam­ eter are rather rare; those in the centi­ meter range are museum pieces. Most of them contain a water solution of various salts, in concentrations ranging from nearly fresh water to highly concen­ h'ated brines. Most also enclose a bubble of gas. When the bubble is small enough to respond to statistical irregularities in the number of molecules striking it, and is free of the inclusion walls, it can be seen to wander continuously in a jerky Brownian movement. It is fascinating to watch such a bubble under the micro­ scope and to think that it has been nerv­ ously pacing its cell for perhaps a billion years. Some inclusions have one or more crystals in the liquid; some are com­ posed of two immiscible liquids; a few, of gas alone. In extremely clear crystals a careful microscopic search may be re­ quired to nd even a single inclusion. Ordinary white minerals such as quartz and calcite may have as many as a bil­ lion inclusions per cubic centimeter. Al­ though uid inclusions in natural crys­ tals are a welcome source of information to the geologist, they may produce dis­ guring aws in gem stones. In arti cial crystals intended for use in electronic circuits inclusions are serious defects."

gems, corundum, ruby, sapphire, inclusions.5

HEALING fissures as inclusions in gemstones are well known Hand have often been described. In spite of this, the question of their origin has not yet been answered. A most valuable hint can be found in papers published by American authors about liquid inclusions in some minerals of the pegmatite series. Here, the aim of numerous investigations was to find out whether or not the liquid inclusions could be used as a geologic thermometer." In this sense researches have been made to prove whether those particular inclusions could supply the desired information about the temperature at which the minerals of the pegmatites, and consequently the pegmatites of certain localities itself, have been formed."

gems, inclusions, spinel, chrysoberyl, quartz, tourmaline, zircon, scapolite, asterism, star, chatoyancy, cat’s eye

corundum, sapphire, India.12, Kashmir.12, inclusions.5, treatments.6, gems

gems, inclusions, corundum, ruby, sapphire, beryl, emerald, spinel

corundum, inclusions.5, gems

corundum, Burma.12, Thailand.12, inclusions.5, gems

gems, amber, Burma, burmite, Sicily, Baltic Sea

An exceptionally comprehensive and learned survey of all phases of the knowledge of amber as then known, and holding its place as the preeminent work on the subject in the English language until the recent appearance of P Rice's Amber: The Golden Gem of the Ages, 1980, which see. Rice's work contains much new information but does not entirely supersede Williamson's highly interesting monograph. The first chapters treat amber in general, discuss classical allusions, nomenclatural problems, the amber routes of antiquity, and the place of amber in anthropology and archeology. Amber is next considered as a substance with remarks on the geology of deposits, and the many inclusions of plant and animal life that have been found in it. Rather strangely, the flow of information on the natural history is here interrupted by a chapter on amber in art, after which the text returns to discussion of the famous amber deposits of the Baltic region, also those in England, and then again, rather jarringly, amber is discussed as a medicinal material and uses in amulets, or other lorical applications. However, from this point, the text treats amber in Sicily, Romania, and Burma, remarks on the similar-sounding ambergris, describes other fossil resins, the making of amber varnish, and amberoid or pressed amber. The bibliography is very extensive, possibly the largest to be assembled up to that time, but the entries lack paginations, and some lack the names of journals from which taken, and others are trivial. Rev K Andree, Bernstein-Forschungen, 3, 1933, 212. Copies are scarce and still much in demand. There is a reprint of same date in sepia-brown cloth, the gold spine Jett usually tarnished to copper.