Chrome chalcedony

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Chrome chalcedony
Mtorolite zimbabwe trimmed.jpg
Zimbabwean chrome chalcedony (known locally as mtorolite). Scale is in centimetres.
General
CategoryOxide mineral
Formula
(repeating unit)
Silica (SiO2)
Crystal system Trigonal or monoclinic [1]
Identification
Formula mass 60 g/mol
Color Emerald green
Cleavage Absent [2]
Fracture Uneven, splintery, conchoidal [2]
Mohs scale hardness6–7 [2]
Luster Vitreous, dull, greasy, silky [2]
Streak White
Diaphaneity Translucent [2]
Specific gravity Usually 2.60, sometimes greater than 2.62 [3]

Chrome chalcedony is a green variety of the mineral chalcedony, colored by small quantities of chromium. [4] Its name is derived from Mutorashanga, a small ferrochrome mining town in Zimbabwe where the mineral was discovered in the 1950s. [5]

Contents

It is most commonly found in Zimbabwe, where it is known as Mtorolite, [6] Mtorodite, [7] or Matorolite. [8] It is also marketed using the trade name, Aquaprase.

Chemical composition

Chrome chalcedony is similar in appearance to the better known chrysoprase, but differs in that whilst chrome chalcedony is colored by chromium (as chromium(III) oxide), chrysoprase is colored by nickel. [4] The two can be distinguished with a Chelsea color filter, as chrome chalcedony will appear red, whilst chrysoprase will appear green. [4] [9] Chrome chalcedony (unlike chrysoprase) may also contain tiny black specks of chromite. [3]

Chrome chalcedony is (together with agate, carnelian, chrysoprase, heliotrope, onyx and others) a variety of chalcedony. This is a cryptocrystalline form of silica, consisting of fine intergrowths of the minerals quartz and moganite. [1]

Locality

Chrome chalcedony (known as mtorolite, mtorodite or matorolite) occurs in Zimbabwe, principally near to the mining town of Mtoroshanga, located on the Great Dyke geological feature. [6] It has also been discovered in western Australia, the Balkans, Bolivia, Turkey and the Ural Mountains. [10]

Ancient history

Chrome chalcedony was widely used in jewellery and seals throughout the Roman Empire. The source of the mineral is unclear, as whilst Pliny the Elder described it as coming from India, no deposits have been found there. It may have come from Anatolia (in modern-day Turkey), where deposits are known to exist. [10]

Chrome chalcedony disappeared from use sometime in the 2nd century. It was only rediscovered when the Zimbabwean deposits were found in the 1950s. [11]

Related Research Articles

<span class="mw-page-title-main">Amethyst</span> Mineral, quartz variety

Amethyst is a violet variety of quartz. The name comes from the Koine Greek αμέθυστος amethystos from α-a-, "not" and μεθύσκωmethysko / μεθώmetho, "intoxicate", a reference to the belief that the stone protected its owner from drunkenness. Ancient Greeks wore amethyst and carved drinking vessels from it in the belief that it would prevent intoxification.

<span class="mw-page-title-main">Amblygonite</span>

Amblygonite is a fluorophosphate mineral, (Li,Na)AlPO4(F,OH), composed of lithium, sodium, aluminium, phosphate, fluoride and hydroxide. The mineral occurs in pegmatite deposits and is easily mistaken for albite and other feldspars. Its density, cleavage and flame test for lithium are diagnostic. Amblygonite forms a series with montebrasite, the low fluorine endmember. Geologic occurrence is in granite pegmatites, high-temperature tin veins, and greisens. Amblygonite occurs with spodumene, apatite, lepidolite, tourmaline, and other lithium-bearing minerals in pegmatite veins. It contains about 10% lithium, and has been utilized as a source of lithium. The chief commercial sources have historically been the deposits of California and France.

<span class="mw-page-title-main">Beryl</span> Gemstone: beryllium aluminium silicate

Beryl ( BERR-əl) is a mineral composed of beryllium aluminium silicate with the chemical formula Be3Al2Si6O18. Well-known varieties of beryl include emerald and aquamarine. Naturally occurring hexagonal crystals of beryl can be up to several meters in size, but terminated crystals are relatively rare. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, pink, and red (the rarest). It is an ore source of beryllium.

<span class="mw-page-title-main">Sapphire</span> Gem variety of corundum

Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name sapphire is derived from the Latin word sapphirus, itself from the Greek word sappheiros (σάπφειρος), which referred to lapis lazuli. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. Red corundum stones also occur, but are called rubies rather than sapphires. Pink-colored corundum may be classified either as ruby or sapphire depending on the locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of special-purpose solid-state electronics such as integrated circuits and GaN-based blue LEDs. Sapphire is the birthstone for September and the gem of the 45th anniversary. A sapphire jubilee occurs after 65 years.

<span class="mw-page-title-main">Tourmaline</span> Cyclosilicate mineral group

Tourmaline is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a wide variety of colors.

<span class="mw-page-title-main">Chalcedony</span> Microcrystalline varieties of silica

Chalcedony ( kal-SED-ə-nee, or KAL-sə-doh-nee) is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Chalcedony's standard chemical structure (based on the chemical structure of quartz) is SiO2 (silicon dioxide).

<span class="mw-page-title-main">Jasper</span> Chalcedony variety colored by iron oxide

Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron(III) inclusions. Jasper breaks with a smooth surface and is used for ornamentation or as a gemstone. It can be highly polished and is used for items such as vases, seals, and snuff boxes. The density of jasper is typically 2.5 to 2.9 g/cm3. Jaspillite is a banded-iron-formation rock that often has distinctive bands of jasper.

<span class="mw-page-title-main">Andalusite</span> Aluminium nesosilicate mineral

Andalusite is an aluminium nesosilicate mineral with the chemical formula Al2SiO5. This mineral was called andalousite by Delamétehrie, who thought it came from Andalusia, Spain. It soon became clear that it was a locality error, and that the specimens studied were actually from El Cardoso de la Sierra, in the Spanish province of Guadalajara, not Andalusia.

<span class="mw-page-title-main">Onyx</span> Banded variety

Onyx is the parallel-banded variety of chalcedony, a silicate mineral. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands. Onyx has parallel bands while agate has curved bands. The colors of its bands range from black to almost every color. Specimens of onyx commonly contain bands of black or white, or both. Onyx, as a descriptive term, has also been applied to parallel-banded varieties of alabaster, marble, calcite, obsidian, and opal, and misleadingly to materials with contorted banding, such as "cave onyx" and "Mexican onyx".

<span class="mw-page-title-main">Uvarovite</span> Chromium-bearing garnet group

Uvarovite is a chromium-bearing garnet group species with the formula: Ca3Cr2(SiO4)3. It was discovered in 1832 by Germain Henri Hess who named it after Count Sergei Uvarov (1765–1855), a Russian statesman and amateur mineral collector. It is classified in the ugrandite group alongside the other calcium-bearing garnets andradite and grossular.

<span class="mw-page-title-main">Chrysocolla</span> Phyllosilicate mineral

Chrysocolla ( KRIS-ə-KOL) is a hydrous copper phyllosilicate mineral and mineraloid with the formula Cu
2 – x
Al
x
(H
2
Si
2
O
5
)(OH)
4
nH
2
O
(x < 1) or (Cu, Al)
2
H
2
Si
2
O
5
(OH)
4
nH
2
O)
.

<span class="mw-page-title-main">Jadeite</span> Pyroxene mineral

Jadeite is a pyroxene mineral with composition NaAlSi2O6. It is hard (Mohs hardness of about 6.5 to 7.0), very tough, and dense, with a specific gravity of about 3.4. It is found in a wide range of colors, but is most often found in shades of green or white. Jadeite is formed only in the subduction zones of continental margins, where rock undergoes metamorphism at high pressure but relatively low temperature.

<span class="mw-page-title-main">Diopside</span> Pyroxene mineral

Diopside is a monoclinic pyroxene mineral with composition MgCaSi
2
O
6
. It forms complete solid solution series with hedenbergite and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull green crystals in the monoclinic prismatic class. It has two distinct prismatic cleavages at 87 and 93° typical of the pyroxene series. It has a Mohs hardness of six, a Vickers hardness of 7.7 GPa at a load of 0.98 N, and a specific gravity of 3.25 to 3.55. It is transparent to translucent with indices of refraction of nα=1.663–1.699, nβ=1.671–1.705, and nγ=1.693–1.728. The optic angle is 58° to 63°.

<span class="mw-page-title-main">Chrysoprase</span> Gemstone variety of chalcedony

Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony that contains small quantities of nickel. Its color is normally apple-green, but varies from turquoise-like cyan to deep green. The darker varieties of chrysoprase are also referred to as prase.

<span class="mw-page-title-main">Demantoid</span> Green gemstone variety of the mineral andradite

Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet group of minerals. Andradite is a calcium- and iron-rich garnet. The chemical formula is Ca3Fe2(SiO4)3 with chromium substitution as the cause of the demantoid green color. Ferric iron is the cause of the yellow in the stone.

<span class="mw-page-title-main">Spessartine</span> Nesosilicate, manganese aluminium garnet species

Spessartine is a nesosilicate, manganese aluminium garnet species, Mn2+3Al2(SiO4)3. This mineral is sometimes mistakenly referred to as spessartite.

<span class="mw-page-title-main">Grossular</span> Garnet, nesosilicate mineral

Grossular is a calcium-aluminium species of the garnet group of minerals. It has the chemical formula of Ca3Al2(SiO4)3 but the calcium may, in part, be replaced by ferrous iron and the aluminium by ferric iron. The name grossular is derived from the botanical name for the gooseberry, grossularia, in reference to the green garnet of this composition that is found in Siberia. Other shades include cinnamon brown (cinnamon stone variety), red, and yellow. Grossular is a gemstone.

<span class="mw-page-title-main">Hydrogrossular</span> Calcium aluminium garnet

Hydrogrossular is a calcium aluminium garnet series (formula: Ca3Al2(SiO4)3−x(OH)4x, with hydroxide (OH) partially replacing silica (SiO4)). The endmembers of the hydrogarnet family (grossular, hibschite, and katoite) depend on the degree of substitution (x):

<span class="mw-page-title-main">Neptunite</span>

Neptunite is a silicate mineral with the formula KNa2Li(Fe2+, Mn2+)2Ti2Si8O24. With increasing manganese it forms a series with mangan-neptunite. Watatsumiite is the variety with vanadium replacing the titanium in the formula.

<span class="mw-page-title-main">Beekite</span>

Beekite is a distinctive form of chalcedony usually associated with silica replacing carbonate minerals in fossils.

References

  1. 1 2 Heaney, Peter J. (1994). "Structure and Chemistry of the low-pressure silica polymorphs". Reviews in Mineralogy and Geochemistry. 29: 1–40.
  2. 1 2 3 4 5 Duda, Rudolf; Rejl, Lubos (1990). Minerals of the World. Arch Cape Press. ISBN   0-517-68030-0(Reference gives data for chalcedony in general.){{cite book}}: CS1 maint: postscript (link)
  3. 1 2 "Insider Gemologist: What Are the Identifying Characteristics of the Different Varieties of Green Chalcedony?". GIA Insider. 7 (13). Gemological Institute of America. 2005.
  4. 1 2 3 Willing, M. J.; Stocklmayer, S.M. (2003). "A new chrome chalcedony occurrence from Western Australia". Gems & Gemology . 23: 265–279.
  5. Murah, Mukundu (June 12, 2023). "Mtorolite Healing Properties, Mineralogy And Uses". The Mineralogie Company. Retrieved December 31, 2023.
  6. 1 2 Cairncross, Bruce (2005). Field Guide to Rocks & Minerals of Southern Africa. Struik. ISBN   1-86872-985-0.
  7. Hey, M. H.; Embrey, P. G. (1974). "Twenty-eighth list of new mineral names" (PDF). Mineralogical Magazine. 39 (308): 903–932. Bibcode:1974MinM...39..903H. doi:10.1180/minmag.1974.039.308.15. Archived from the original (PDF) on 2015-06-10. Retrieved 2009-01-22.
  8. Hey, M. H. (1970). "Twenty-sixth list of new mineral names" (PDF). Mineralogical Magazine. 37 (292): 954–967. Bibcode:1970MinM...37..954H. doi:10.1180/minmag.1970.037.292.19. Archived from the original (PDF) on 2015-06-10. Retrieved 2009-01-22.
  9. O'Donoghue, Michael (2006). Gems. Butterworth-Heinemann. ISBN   0-7506-5856-8.
  10. 1 2 Lule-Whipp, Cigdem (2006). "Chromium Chalcedony from Turkey and Its Possible Archeological Connections" (PDF). Gems & Gemology: Proceedings of the 4th International Gemological Symposium & GIA Gemological Research Conference, San Diego, California. Vol. 42. p. 115. Archived from the original (PDF) on 2008-09-20. Retrieved 2009-01-22.
  11. Thoresen, Lisbet. "Ancient Glyptic Art Gem Engraving and Gem Carving". Archived from the original on 2008-12-26. Retrieved 2009-01-13.