Minerals and Metals in Ancient India v2.c47: Appendix A: Scientific Information on the Minerals used in the Ancient Period of Human History
Minerals and Metals in Ancient India v2.c47
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Appendix A: Scientific Information on the Minerals used in the Ancient Period of Human History
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*Actinolite* : Means ray in Greek. Calcium-magnesium-iron amphibole Ca₂ (Mg, Fe)₅ (OH)₂ (Si₄O₁₁)₂. Ca-Mg amphibole is tremolite (white). Due to iron, actinolite is dark-green. Mixture of the two is asbestos (does not contain hardening aluminium). Aluminium makes the structure hard and results in jade family of numerals (hardness 6-7). *Nephrite* may be white jade or green due to iron and manganese. The apple-green and emerald green colour of *jadeite* is due to the presence of chromium. It could be mauve or light blue also. The black colour of *chloromelanite* is due to excess concentration of iron in the structure. *Smaragdite* is near actinolite in composition but contains some aluminium. It is thin-foliated and has a light grass-green colour. The word for green is *smaragdus* in Latin and *smaragdos* in Greek.
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*Adamantine Spar* : see Corundum
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*Adularia* : see Feldspar
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*Agate* : see Quartz
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*Alabaster* : see Gypsum
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*Albite* : see Feldspar
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*Almandine* : see Garnet and Ruby
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*Almandite* : see Garnet
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*Amazon Stone* : see Feldspar **Amber** : This is a fossil resin consisting of oxygenated hydrocarbons. C:H:O ratio is approximately 10 : 16 : 1. Part of it yields succinic acid. Colour yellow, sometimes reddish, brownish or whitish. Sometimes fluorescent and luster resinous. Melts at 250-300°C. Of vegetable origin, altered by fossilization, found on the shores cast up by the waves after a heavy storm. Amber was early known to the ancients as *electrum* (electrical susceptibility) whence the word electricity was derived. The word *electrum* was used for gold-silver alloy also.
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**Amethyst** : see Corundum and Quartz
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**Andradite** : see Garnet
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**Aquamarine** : see Beryl
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**Asbestos** : see Actinolite
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**Aventurine** : see Feldspar and Quartz
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**Balas Ruby** : see Ruby
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**Beryl** : Be₃Al₂(SiO₃)₆ sometimes a little Na, Li or Cs replacing Be. Hardness 7.5-8.0. Several varieties. Emerald bright green contains little chromium. Pure beryl hexagonal prism, pale green.
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**Aquamarine** : is bluish-green. Heliodor is golden beryl, yellow due to trace of iron. Beryl is harder than hexagonal apatite and green tourmaline. Differs from Chrysoberyl by its form, see Chrysoberyl which is BeAl₂O₄. Beryl can be blue like sapphire (Al₂O₃) just as oriental emerald (Al₂O₃) looks like emerald (beryl) in its green colour.
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**Bitumen** : see Coal
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**Blood-Stone** : see Quartz
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**Bone Turquoise** : see Turquoise
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**Borax** : Composition Na₂B₄O₇, 10H₂O Hardness 2-2.5 white. Vitreous to resinous luster. Obtained from evaporation of saline lakes and salt deposits in Kashmir and Tibet. Used as flux for soldering, as antiseptic, washing etc. Called *burag* in Arabic which included niter sodium carbonate, also natron of the Egyptian crude borax known as tincal by the Europeans.
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**Cacholong** : see Quartz
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**Calcite** : CaCO₃. Hardness 3. Highly birefringent. In crystal form also known as Calc Spar, Iceland Spar, Satin Spar etc. In granular massive to crypto-crystalline kind occurs as rock limestone, marble (meta-morphic, higher density) and chalk. Various colours due to impurities. Onyx marble (banded) also known as *oriental alabaster*. Chalk, composed of the shells of minute sea organisms, leaves a trace on a board.
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*Dolomite* is CaMg(CO₃)₂ constituent of dolomitic limestone.
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*Carbuncles* : see Garnet
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*Carnelian* : see Quartz
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*Cassiterite* : Main ore of tin. SnO₂. Hardness 6-7. sp. gr. 6.8-7.1 Adamantine luster : Colour brown or black. Occurs in granitic rock or pegmatites. Also alluvial washings. Occurs in Malay Peninsula, coast of Sumatra etc.
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*Cat's Eye* : see Chrysoberyl and Quartz
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*Ceylonite* : see Ruby Spinel
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*Chalcedony* : see Quartz
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*Chalcocite* : Cuprous sulphide. Cu₂S
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*Chalcopyrite* : Copper Pyrites. Brass Yellow tarnished. CuFeS₂
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*Chalk* : see Calcite
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*Chloromelanite* : see Actinolite
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*Chrysoberyl* : BeAl₂O₄. Hardness 8.5. Tabular and not hexagonal crystallization. Ordinarily pale green but trace impurity of iron makes it yellow. *Chryso* means golden. *Cat's eye* has greenish colour and exhibits a fine chatoyant effect. Available in Sri Lanka.
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*Chrysolite* : This is a group of orthosilicate minerals of general formula R₁ᴵᴵR₂ᴵᴵ(SiO₄) where R₁ and R₂ are usually combinations of Mg, Fe, Ca, Mn etc.
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The chrysolite sub-group include *Olivine* and *Peridot* having Mg and Fe in the structure, the Mg/Fe ratio varying from 16 to 2. There is some replacement of Si by Ti. Olivine is olive-green, sometimes bottle-green or yellowish green. *Peridot* is clear fine green. *Chrysolite*, named from chryso (gold) is yellow. E.S. Dana commented that “the *chrysolithus* of Pliny was probably our topaz; and his topaz our chrysolite”.
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*Chrysoprase* : see Quartz
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*Cinnabar* : HgS. Only common mineral of mercury. Bright red to reddish brown in colour and vermilion streak. Occurs in slates, shales, sandstones, mixed with clay, bitumen. Major occurrence in Spain, Dutch Guiana, China etc. The name ‘cinnabar’ is supposed to come from India, where it is applied to the red resin, dragon's blood, zinzifrah in Persian.
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Theophrastus mentioned cinnabar yielding quicksilver (mercury).
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*Citrine* : see Quartz
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*Coal* : Plant residue converted into carbonaceous material. Anthracite intermediate product gradually converted to bituminous coal containing hydrocarbon oil or tar yielded during distillation.
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*Coral* : Sub-marine calcareous growth of *Isis Nobilis* insect.
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*Corundum* : Aluminium oxide. Al₂O₃. White if pure. Many varieties of different colours due to traces of specific impurities. Sapphire is blue (due to Ti, Fe & Co). True or Oriental Ruby is red. Oriental Topaz Yellow. Oriental Emerald green Amethyst purple. The term sapphire is used in general sense for all colours except red. Asteriated or *Star Sapphire* shows stallate opalescence or asterism which is due to the presence of minute cylindrical cavities which lie parallel to the prism planes. Adamantine Spar from India is dark to translucent corundum, looking greenish or bluish by transmitted light. Emery is granular corundum. May be black or grey due to intimate association of magnetite or hematite.
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The name originated from the Indian word *kuruvinda* or *karundaka*.
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*Diamond* : Pure carbon C. Hardness 10 in Moh’s Scale (highest). Harder and heavier (sp. gr. 3.52) than quartz. Luster adamantine to greasy. Colour white or sometimes yellow, blue due to impurities. High refractive index. Sometimes shows phosphorescence when rubbed. When full of flaws, used chiefly as abrasive. If flawless, used as gem. Weighed in carats (0.2 g).
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Diamond works started in Brazil during the early part of the eighteenth century and in South Africa during 1867. Before that India was the chief producer.
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The word originated from the greek word *adamas*, alluding to its hardness.
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*Dolomite* : see Calcite
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*Electrum* : see Amber and Gold
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*Emerald* : see Beryl
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*Emerald Oriental* : see Corundum
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*Emery* : see Corundum
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*Essonite* : see Garnet
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*Feldspar* : Group of minerals. Three important sub-classes:
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*Orthoclase*, α monoclinic; *Microcline*, β triclinic both KAlSi₃O₈ where K may be partly replaced by Na; and third *Albite* NaAlSi₃O₈ and Plagioclase series, Na partly replaced by Ca in the structure.
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*Adularia* is a low temperature variety of pure orthoclase. Crystallisation at high temperature, above 900°C, produces *Sanidine*.
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Beautiful green *Amazonstone* is a variety of microcline, has the usual triclinic twinning striations and grating structure.
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*Aventurine feldspar* is a variety of albite with reddish reflection from certain planes due to thin lamellae of hematite. *Perthite* is a flesh-red aventurine feldspar consisting of inter-laminated orthoclase and albite. *Microcline-perthite* is a similar interlamination of microcline and albite. When the structure is discernible only with the help of the microscope, it is called *microperthite*.
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*Moonstone*, available in Sri Lanka, is a microperthitic to sub-microperthitic intergrowth of orthoclase and albite in an arrangement of thin layers exhibiting a pearly opalescent reflection or schiller or a delicate play of colours. It has beautiful blue bloom and lovely sheen.
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*Sunstone* is a variety of oligoclase, Na-Ca feldspar containing little K and Ba feldspar. A play of colour is a common character, fire-red, yellow, blue, green etc. This is due to interference of light, caused by reflection from thin lamellar inclusions of various minerals such as hematite, goethite etc. Associated with granite and igneous rocks.
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*Fluorite* : Fluorspar. CaF₂ Hardness 4. Octahedral or dodecahedral crystals. Luster vitreous. Colour usually white but varies over a wide range — violet, blue, yellow, red — even in different portions of the same specimen. Modified by heat, pressure, radiation etc. which also cause phosphorescence. High birefringence. Used as flux, in metallurgy, in making opalescent glass, as ornament gems.
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*Galena* : PbS. Luster metallic. Colour and streak grey. Heavy, sp. gr. 7.4-7.6. Hardness 2-2.5. Sometimes contains native silver and gold.
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*Garnet* : Orthosilicate group of Minerals. Latin *granatum* (= pomegranate). RII₃RIII₂ (SiO₄)₃ in which RII could be Ca, Mg, FeII, MnII etc. and RIII could be Al, FeIII, Cr. Ti etc. Dodeca- and trapezo-hedron crystals.
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*Grossularite* : Essonite or *Hessonite*. Cinnamon-stone. These are Calcium-Aluminium garnets with some replacements by FeII, FeIII, Cr. Variable colour. The name grossularite comes from gooseberry (pale green). Hessonite is cinnamon-coloured. Available in Sri Lanka it has a variety called *Hyacinth* (inferior) less in hardness than true hyacinth, coloured yellow to yellowish-red. A particular variety of zircon is also called Hyacinth.
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*Pyrope* : means fire-like. It is a magnesium-aluminium garnet with some replacement by Ca, Fe and Cr. Coloured deep-red often transparent.
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*Almandite* : *Almandine*. The Alabandic Carbuncles of Pliny were so-called because these were cut and polished at Alabanda. Hence the modern name almandine or almandite which is an iron (Feᴵᴵ) — aluminium garnet with some replacement by Mg and Feᴵᴵᴵ. This is the most common variety usually coloured brownish red and widely found in India and Sri Lanka. *Andradite* is Ca-Al (blackish) garnet.
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*Grossularite* : see Garnet
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*Gold* : Au. Yellow. Metallic luster, sp. gr. 19.33 when pure. At present obtained from quartz veins, in the ancient period from alluvial washings.
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*Electrum* is pale yellow to yellowish white. Lower sp.gr. (12.5-15.5) Gold containing 18-36 p.c. silver. The word in Greek means also amber.
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*Graphite* : C. Carbon. Very soft. Occurs with nephelite/syenite in India, in pegmatite — veins in Sri Lanka.
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*Gypsum* : CaSO₄, 2H₂O. Greek *gypsos* (= plaster). Hardness 1.5-2.0 Varieties: Crystallized or *Selenite* is colourless or transparent. *Alabaster* is a massive fine-grained variety, white or delicately shaded. *Rock gypsum* may have silica, clay or calcium carbonate as impurities.
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*Halite* : *Rock Salt*. Sodium chloride NaCl. Cubic crystals white. Typical taste. May contain Mg, K Salts. Perfect cubic cleavage. Soft. Hardness 2-3. Formed due to evaporation of sea water. Associated with sedimentary rocks. Enormous deposit in the Salt Range of Punjab, India, at Khewra etc.
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*Heliodor* : see Beryl
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*Heliotrope* : see Quartz
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*Hematite* : Iron sesqui-oxide. Fe₂O₃. Greek *haimatitis* (= blood red). Colour steel grey to reddish brown. It may be specular with metallic luster, compact columnar or red ocherous. The most important iron ore.
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*Hessonite* : see Garnet
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*Hyacinth* : see Garnet and Zircon. Name from purplish blue hyacinth flower.
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*Iaspis* : see Jasper *Iceland spar* : see Calcite
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*Iolite* : Cordierite. Mg₂Al₄Si₅O₁₈. Sometimes Mg replaced by Fe²⁺. Shades of blue. Sri Lanka has a transparent variety in small rolled masses of an intense blue colour, the *saphir d'eau* of jewellers. 'Iolite' stands for violet stone. The name Cordierite is after Cordier, the French geologist.
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*Jade* : see Actinolite
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*Jadeite* : see Actinolite
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*Jargon* : see Zircon
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*Jasper* : see Quartz. The name from Latin *iaspis*, Persian *iashm* and *jashp*.
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*Kaolin* : China-clay. Name from the Chinese hill Kauling. Phyllosilicate. Al₄Si₄O₁₀(OH)₈. Dull earthy-white. Soft. Hardness 2-2.5. Product of decomposition of feldspar, granite etc. May be associated with quartz, iron oxide etc. Pure variety for pottery, porcelain or Chinaware etc.
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*Lapis Lazuli* : This richly coloured blue material is a heterogeneous mixture of Sodalite group of minerals:
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Lazurite 3Na₂Al₂Si₂O₈, 2Na₂S (Chief constituent)
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Haüynite 3Na₂Al₂Si₂O₈, 2CaSO₄ and
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Sodalite 3Na₂Al₂Si₂O₈, 2NaCl
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and also several other mineral phases arising out of limestone-granite contact metamorphism.
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When powdered, constitutes the durable paint called *ultramarine*.
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Massive lapis lazuli widely used in the past as gems, for making vases, furnitures, mosaics etc.
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The name from Persian *lazhward*, Sanskrit *rājāvarta*.
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*Lazurite* : see Lapis Lazuli
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*Limestone* : see Calcite
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*Lodestone* : see Magnetite
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*Löllingite* : Iron diarsenide. FeAs₂. Associated with Fe₃As₄ (leucopyrite), and arsenopyrite FeAsS Luster metallic. Colour silver white to steel grey. Name from Lolling, Austria.
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*Magnetite* : Iron sesquioxide. FeᴵᴵFeᴵᴵᴵ₂O₄ or Fe₃O₄. Named after the Greek discoverer Magnes. Strongly magnetic of special variety Lodestone possesses polarity and acts like a magnet. Ordinary magnetite is merely attracted by a magnet.
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*Marble* : see Calcite
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*Melantite* : Green Vitriol FeSO₄, 7H₂O
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*Mica* : see Muscovite. Name from Latin *micare* (to shine).
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*Microcline* : see Feldspar
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*Moonstone* : see Feldspar
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*Muscovite* : Orthosilicate of Al and K. Sheet structure. Based cleavage. This is common Mica.
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*Nephrite* : see Actinolite
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*Niter* : Sodium nitrate NaNO₃. Chilean Saltpetre. Also Potassium nitrate. KNO₃. Forms abundantly in certain soils by the action of bacteria upon animal remains. In great quantities in the desert region of northern Chile. Also in the ancient world, India, Egypt, Persia etc.
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*Odontolite* : see Turquoise
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*Olivine* : see Chrysolite. The name from olive green colour.
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*Onyx* : see Quartz. Greek word means claw, veined gem.
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*Onyx Marble* : see Calcite
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*Opal* : see Quartz, Sanskrit word *upala*, precious stone.
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*Oriental Alabaster* : see Calcite
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*Oriental Amethyst* : see Corundum
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*Oriental Emerald* : see Corundum
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*Oriental Ruby* : see Corundum
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*Oriental Topaz* : see Corundum
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*Orpiment* : Arsenic Trisulphide As₂S₃. Soft. Colour lemon yellow of different shades. Name a corruption of Latin name *auripigmentum* or golden paint. Also used as a depilatory agent. Associated with *Realgar* which is Arsenic Monosulphide, AsS. *Realgar* is sectile, soft resinous luster. Colour aurora-red or orange-yellow. Found with stibnite, lead, silver and gold. Gives brilliant white light when ignited with saltpetre. Disintegrates on exposure ‘*Realgar*’ name from *Rahj al ghār* (Arabic), powder of the mine.
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*Orthoclase* : see Feldspar. Greek for straight and fracture.
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*Peridot* : see Chrysolite *Perthite* : See Feldspar
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*Piotine* : see Talc
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*Plasma* : see Quartz, Greek word for things formed or molded, name used probably because the mineral was used for intaglios.
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*Pyrite* : FeS₂. Pale brass yellow. Metallic luster, splendent to glistening. Hardness 6-6.5. Harder than chalcopyrite. Associated with copper and gold. On the surface altered to a cellular mass of limonite, on iron gossan and sulphuric acid, usually by bacterial action. The name pyrite is derived from fire, and alludes to the sparks formed when the mineral is struck with a hammer.
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*Pyrope* : see Garnet
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*Pyrophyllite* : Talc like. Soft. Resembles Steatite or French Chalk. White or yellowish. Peraly luster. Al₂Si₄O₁₀(OH)₂. Phyllosilicate.
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*Quartz* : SiO₂. Hardness 7. Many colours due to impurities. Name from Saxon word querkluftertz, meaning cross-veined ore.
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A. Phenocrystalline or Vitreous Varieties *Rock Crystal*. Colourless. Star quartz, *Amethyst quartz*, purple or bluish violet due to Mn. Yellow quartz (*false topaz*) or Citrine. *Cat’s eye quartz* like chrysoberyl. *Jasper* is impure opaque coloured quartz commonly red or yellow. *Aventurine (quartz)* is spangled with scales of mica, hematite or other mineral.
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B. Cryptocrystalline quartz. Contains variable proportions of water and colloidal silica.
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*Chalcedony*. SiO₂, nH₂O. Wax like luster. Many varieties:
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(i) *Carnelian*. Sard pale to deep red chalcedony.
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(ii) *Chrysoprase*. Apple-green due to nickel content.
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(iii) *Plasma*. Bright to emerald green. *Heliotrope* or *Blood-stone* is Plasma with small spots of Jasper (like drops of blood).
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(iv) *Agate*. Banded, different coloured chalcedony. Silica deposited in bands — stright or waving.
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(v) *Onyx*. Like agate of different colours, but the layers in even planes, and the banding straight, and hence its use for cameos.
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(vi) *Sardonyx*. Onyx with layers of sard on carnelian, i.e., red with white or black bands.
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*Flint* and *Chert* are related to chalcedony. Sandstone is quartzsand conglomerate rock. Opal is amorphous colloidal silica in massive form. Luster vitreous to resinous. Play of colour. Thin curved lamellae of particles in the matrix have differential refractive indices and cause play of colour on rotation. Cacholong is opaque, bluish white or porcelain white opal.
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*Pearl* : Nacre consisting of calcium and protein layers around foreign objects inside the oyster, *Pinctada Vulgaris*.
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*Realgar* : see Orpiment
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*Rock Crystal* : see Quartz
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*Rock Salt* : see Halite
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*Rubicelle* : see Ruby
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*Ruby* : See Corundum Al₂O₃; for true or oriental Ruby colour red. Latin rubeus (red).
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There is another variety of Ruby belonging to a different family: *Spinel* Group RᴵᴵRᴵᴵᴵO₄. *Ruby Spinel* is a magnesia alumina spinel MgAl₂O₄. This is clear red on account of some association of chromium in the structure. There may be little iron also. Some varieties are: (a) *Spinel-Ruby*, deep red; (b) *Balas-Ruby*, rose red; (c) *Rubicalle*, yellow or orange red; and (d) *Almandine*, violet, which is different from the almandine in the *Garnet* family. *Ceylonite* is Fe-Mg Spinel, opaque, dark green brown or black. Spinel Rubies are distinguished by their octahedral form, hardness and infusibility. Zircon has a higher specific gravity. True or Oriental Ruby is harder and is distinguished optically. Garnet is softer and fusible.
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*Sal Ammoniac* : Ammonium Chloride. NH₄Cl. White incrustation, sublimation product around volcanoes.
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*Sandstone* : see Quartz
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*Sanidine* : see Feldspar
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*Saponite* : see Talc
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*Sapphire* : see Corundum
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*Sapphire Asteriated/star* : see Corundum. Sanskrit equivalent Sanipruja?
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*Sard* : see Quartz. Name either from Sardis, capital of ancient Lydias or from Persian word (sered = yellow-red).
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*Sardonyx* : see Quartz
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*Satin Spar* : could be Calcite or Gypsum
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Appendix A
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Selenite : see Gypsum. Greek word for moon, alludes to reflection.
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Serpentine : Magnesium silicate. Phyllosilicate. Mg₆Si₄O₁₀(OH)₈. Ornamental stone. Leek-green. Smooth, greasy. Massive, lamellar, thin foliated or fibrous like Chrysolite. Also called Chrysotile. Harder than talc. Hardness 3-5. Latin serpens ( = snake), in allusion on to the surface pattern of some serpentinite rocks, which resemble the skin of a serpent.
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Shell : Conch-shell : The Indian Variety of śaṅkha, Turbinella Pyrum Linn., and the related genus produce hollow tubular piece, used for bangles, and the inner columella (kṛśan) used for making beads.
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Silver : Ag. Ductile and malleable metal. Hardness 2-3. Sp. gr. 10-11 pure 10.5. Colour white. Associated with gold and copper in rocks.
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Smaragdite : see Actinolite
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Soapstone : see Talc
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Sodalite : see Lapis Lazuli
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Spinel Ruby : see Ruby
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Starlite : see Zircon
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Steatite : see Talc
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Stibnite : Antimony trisulphide. Sb₂S₃. Luster metallic. Highly splendent on cleavage. Colour lead-grey to steel grey, subject to blackish tarnish, sometimes irridescent. Hardness 2. Harder than graphite. Occurs with quartz, galena etc. Chief deposits in Hunan and other areas of central and southern China, Algeria, Mexico etc.
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Metastibnite is an amorphous brick-red deposit of Sb₂S₃ occurring with cinnabar and arsenic sulphide.
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Sulphur : Element. S. Soft, yellow, resinous luster, typical smell. Formed in volcanic, bacterial activity etc. Associated with gypsum, limestone.
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Sunstone : see Feldspar
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Sylvite : Potassium Chloride. KCl. Sometimes contains sodium chloride. White, Vitreous luster. Tastes like common salt but bitter.
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Talc : Phyllosilicate. Mg₃Si₄O₁₀(OH)₂. Faint green, soapy. One of the softest minerals. Hardness 1. Perfect, basal cleavage. Sectile, greasy. Pearly luster Talc could be foliated. The massive variety is called Steatite or Soapstone. This is coarse granular and greyish green. Yields variable quantity of water on ignition. It occurs in large amount in India and China.
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A related mineral is Saponite or Piotine. Commonly massive. In nodules, or filling cavities. Soft like fat, hence ‘piotine’, like soap hence ‘saponite’. This is hydrous silicate of magnesium and aluminium, the latter partly replacing Mg and partly Si in the sheet structure. Colour white to dark. Gives out water very readily on heating and then darkens. This is unlike talc.
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*Tincal* : see Borax
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*Topaz* : It has the formula [Al (F,OH)₂] AlSiO₄ with variable proportions of F and OH. In an extreme case, it could be (AlF)₂SiO₄. Prismatic crystals. Hardness 8. Vitreous luster. Colour is usually straw yellow, wine yellow. Impurities may cause diverse colours such as grey, green, blue, red etc. Often contains inclusions of CO₂. On heating, the mineral may assume a pink or red hue, resembling the Balas ruby. On heating with cobalt solution it becomes blue.
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The name topaz is from an island in the red sea as stated by Pliny. The topaz of Pliny however is not true topaz, since it ‘yielded to the file’ and therefore not very hard. Pliny and earlier writers included topaz under the name chrysolite.
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*Topaz False* : see Quartz
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*Topaz Oriental* : see Corundum
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*Tourmaline* : Usually bluish-black, vertically striated prismatic, vitreous to resinous luster. May be of different colours — black, blue, green, red — due to impurities. Birefringent, pyro-electric.
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This is a complex sub-silicate of boron and aluminium, with either Mg, Fe or alkali metals (and sometimes fluorine) present. The formula has been variously claimed as H₉Al₃(B.OH)₂Si₄O₁₉ or 4R₆Al₂(SiO₄)₃.R₆Al₁₂(B₂O₅)₃. The composition is still uncertain.
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Yellow and brown crystals come from Sri Lanka. The name turmalin from Turamali in Ceylonese (applied to zircon by jewellers of Sri Lanka) was introduced into Holland in 1703, with a lot of gems from from Sri Lanka.
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*Tremolite* : see Actinolite
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*Turmali* : see Tourmaline
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*Turquoise* : This is a hydrous phosphate of aluminium and copper; may be considered to be an aggregate of orthophosphoric acid molecules hooked with (CuOH) and Al(OH)₂ radicals. A typical formula is H₅ (CuOH) [Al (OH)₂](PO₄)₄. Waxy luster. Colour sky blue, bluish green. Has a secondary origin through reaction of copper mineral and feldspar aluminium with apatite or organic phosphorous. Much of the turquoise used in the ancient world was odontolite or bone-turquoise formed from fossil bone. In the Harappan period, much of turquoise came from Persia, near Nishapur in Khorasan. This was found in narrow seams or in irregular patches in porphyritic trachyte, associated with limonite. A greenish blue variety comes from Siberia. Turquoise is the French word for Turkish. The mineral travelled to the West from Persia through Turkey.
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*Ultramarine* : see Lapis Lazuli
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*Vermilion* : see Cinnabar
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*Vitriol Blue* : CuSO₄, 5H₂O. Obtained through bacterial oxidation of chalcopyrite and other copper minerals.
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*Vitriol Green* : Melantite. FeSO₄, 7H₂O
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*Zircon* : This is the orthosilicate of zirconium. ZrSiO₄. This may contain some hafnium and little Fe₂O₃, the latter giving it a brownish colour. Pure zircon is colourless, adamantine in luster. But unlike diamond, it is birefringent and less hard (7.5). Its density is 4.68-4.70.
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Jargon is a name given to the colourless or smoky zircons of Sri Lanka, in allusion to the fact that while resembling the diamond in luster, they are comparatively worthless; thence came the name Zircon. An alternative theory is that the name was derived from Zarqun (Arabic) which is from Persian Zar (= gold) and qun (= colour). Hyacinth is the orange, reddish and brownish transparent variety of zircon, used as gem. A particular mineral of the Garnet family is also called Hyacinth. Zircon, when exposed to hot fumes from a solution of cobalt nitrate and potassium ferro-cyanide gives blue artificial gem starlite.
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The occurrence of *Vaikranta* is described in the *Rasa-ratna-samuccaya* along with its varieties. It is said to be a semi-precious stone, and is often confused with the diamond. It is formed from the essence of the eight metals, and is found in the same mines as the diamond. This is found in narrow seams or in regular patches in the mines associated with diamonds. A variety of *Vaikranta* is also mentioned in the *Rasa-ratna-samuccaya* as being of the colour of the *Japa* flower.
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*Vaikranta* is chemically Fe₃O₄ (magnetite).
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It is a variety of iron ore. This mineral is often found in the form of octahedrons, and is sometimes confused with the diamond. It is described as having eight facets and being hard (8.5). It is said to be a gem given to the gods, and is often used as a substitute for the diamond. According to the *Rasa-ratna-samuccaya*, it is a gem of the gods.
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*Vaikranta* is also described as being of the colour of gold. It is said to be a gem of the gods, and is often used as a substitute for the diamond. It is also described as being of the colour of the *Japa* flower.
Linked texts (1)
- Naturalis historia — C. Plinius Secundus, Latin