The Olivine Group, LLC is a Missouri Limited-Liability Company filed on August 30, 2019. It has also been found in metamorphosed Fe‐rich sediments. Olivine is sometimes available from pallasites but the value of the pallasite itself is usually greater than the olivine it contains and little is available from that source. The gem market is now dependent on deposits in Arizona, New Mexico, Norway and Burma. The deposit, probably genetically unique, is related to the opening of the Red Sea rift, thought to be the product of high‐temperature hydrothermal activity. Crystalline material may be transparent to translucent. The name olivine was given by A.G. Werner in 1790, alluding to the common olive‐green colour. In 1958 the mines were nationalized by the Egyptian Government, but mismanagement saw the breakdown of operations. Little needs be said about the curation of olivine. 3). Intermediate members of this and other series are nominated in the same way. The name was derived from the Greek for gold and stone and was formerly used to describe any green‐coloured gems, including olivine, as used by J.G. Thus, it is a type of nesosilicate or orthosilicate. Tephroite forms a series with fayalite. Unfortunately the famous deposit on the Egyptian Island of Zarbarjed (now St John's Island) off the western shores of the Red Sea, 50 miles south of Berenice at 23°36′16″N and 36°11′42″E is no longer available. 4), which is the rarer of the two species, is stable in the presence of SiO2 and can thus occur in such igneous rocks as syenites, trachytes, etc. Although used on the continent as a species name, in Britain the name peridot is used almost entirely as a jewellery term. It was certainly well known in ancient Egypt, the gem being actively worked on the island using slave labour. Providing the ion size is <15 per cent, substitution is possible in the lattice. Continuing basaltic extraction from the mantle led to the intrusion of large dolerite sills at the contact zone between former masses of peridotite (now serpentized) and sedimentary horizons. General considerations. percent of forsterite (Fo) and fayalite (Fa) components, which equals, for example, Fo87= Fa13. The company's filing status is listed as Active and its File Number is LC001665599. Terrestrial material, as kept in a mineral collection appears to be stable long‐term. It has been suggested that the small amount of Ni present in analyses could be responsible for the dominant green colour of olivine. The second member of the group was named tephroite in 1823 by Johann Friedrich August Breithaupt. The name is now used as a group name. Apart from geological reasons, some deposits are banned from collectors for economic or political reasons. Excellent olivine has been found in the centres of volcanic ‘bombs’ present in the seventeenth and eighteenth century lava flows on Lanzarote in the Canary Islands. The refractive indices and densities of the humite-group minerals increase progressively from norbergite to clinohumite; they are restricted mainly to metamorphosed and metasomatized limestones and dolomites, and to skarns associated with ore deposits at contacts with acid plutonic rocks. While olivine is widespread in anhedral masses as an important component of igneous rocks on a global scale, occurrences that yield collectable masses, and even more uncommonly, euhedral crystals, are rare. Mineralogical inclusions have been identified in olivine, for example, Mg‐rich calcite in forsterite. In the (Mg, Fe)-olivines there is complete solid solution between Mg 2 SiO 4 (forsterite) and Fe 2 SiO 4 (fayalite); similarly the (Fe, Mn)-olivines form a continuous series. Colour can be misleading. Even green bottle glass has been used, and stones with a higher ratio of Fe have been improved by heating. The process is often initiated along channels in the structure parallel to the {010} directions. Rod‐shaped ilmenite inclusions in the olivine of a peridot in the Swiss Alps and carbon inclusions in chrondritic meteorites. To promote such merit it was chosen as the birthstone for the month of August where mythology maintains that it provided physical tenacity and strength of nerves to the wearer. 1). Heddle, in his Mineralogy of Scotland reported olivine (unspecified) in crystals up to 45 mm across at Rudha na Clach on Loch Bracadale on the Island of Skye, ‘embedded in basalt associated with zeolites and calcite’. Photo: Courtesy of O. Johnsen, Geological Museum, Copenhagen. It is also an important constituent of lunar basalts and meteorites, especially pallasites, which have a high proportion of olivine in their composition in a nickel‐iron matrix. Olivines with independent SiO2 tetrahedra are susceptible to hydrothermal alteration, low‐grade metamorphism and aerobic weathering.
2020 olivine group members