Chrome Chalcedony
Chrome Chalcedony is a rare green, a chromium-bearing variety of Chalcedony. It is the product that is same called “Mtorodite” or “Mtorolite” following the discovery near the mining town of Mtoroshanga, Mashonaland West, Zimbabwe and material called “Chiquitanita” after the source in the Chiquitos Province, Bolivia.
By any of these true names; Chiquitanita, Mtorodite, Mtorolite or Chrome Chalcedony, all of them are a variety of Chalcedony coloured by small degrees of chromium. They are all similar in appearance towards the better known Chrysoprase, but differ in that Chrome Chalcedony is coloured by chromium while Chrysoprase is coloured by a nickel. The two can be distinguished by a Chelsea colour filter, as Mtorodite (chrome Chalcedony) will appear red, and Chrysoprase will appear green. Chrome Chalcedony, unlike Chrysoprase, may also contain tiny black specks of chromite. Chrome Chalcedony, along with Agate, Carnelian, Chrysoprase, Heliotrope (Bloodstone), Onyx and other people, are all types of Chalcedony which is a cryptocrystalline form of Quartz.
Chrome Chalcedony was widely utilized in jewellery and seals throughout the Roman Empire. Its usage that is earliest seems to have occurred around the first century AD and then disappeared from use sometime in the second century. The way to obtain this material is ambiguous. Pliny it was described by the Elder as coming from India, but no deposits have actually been found there. It may have come from Anatolia (in contemporary Turkey) where deposits are proven to exist day. Chrome Chalcedony was not “discovered” again until 1955 near the mining town of Mtorochanga in Zimbabwe. A quantity that is small of sources of chromium-bearing Chalcedony has now been reported since the mid-1980’s. It has also been discovered in Western Australia; Saricakaya, Eskisehir, Central Anatolia, Turkey; Ural mountains, Russia and from Rincón del Tigre, Chiquitos Province, Santa Cruz Department, Bolivia.
| Category: | Oxide mineral |
| Chemical Formula: | SiO2 + Cr |
| Silicon Dioxide (Quartz) + Chromium | |
| Crystal System: | Trigonal |
| Color: | Emerald green |
| Mohs scale hardness: | 6 – 7 |
| Luster: | Vitreous, dull, greasy, silky |
| Specific gravity: | 2.55 to 2.70 |
| Refractive Index: | 1.530 to 1.543 |
| Transparency: | Translucent, Opaque |
| Optical Character: | Uniaxial/+ |
| Fracture: | Conchoidal, Granular |
| Birefringence: | 0.003 to 0.009 |
