Peridot (/ˈpɛrɪdɒt/ or /ˈpɛrɪdoʊ/) (sometimes called chrysolite) is gem-quality olivine and a silicate mineral with the formula of (Mg, Fe)2SiO4. As peridot is a magnesium-rich variety of olivine (forsterite), the formula approaches Mg2SiO4.
Contents
1 Etymology
2 Appearance
3 Occurrence
3.1 Geologically
3.2 In meteorites
4 Gemology
5 Gallery
6 References
7 External links
Etymology
The origin of the name peridot is uncertain. The Oxford English Dictionary suggests an alteration of Anglo–Norman pedoretés (classical Latin pæderot-), a kind of opal, rather than the Arabic word faridat, meaning "gem".
The Middle English Dictionary's entry on peridot includes several variations: peridod, peritot, pelidod and pilidod — other variants substitute y for the is seen here.[1]
The earliest use in England is in the register of the St Albans Abbey, in Latin, and its translation in 1705 is possibly the first use of peridot in English. It records that on his death in 1245, Bishop John bequeathed various items, including peridot, to the Abbey.[2]
Appearance
Peridot is one of the few gemstones that occur in only one color: an olive-green. The intensity and tint of the green, however, depends on the percentage of iron in the crystal structure, so the color of individual peridot gems can vary from yellow, to olive, to brownish-green. In rare cases, peridot may have a medium-dark toned, pure green with no secondary yellow hue or brown mask.[3]
Occurrence
Geologically
Olivine, of which peridot is a type, is a common mineral in mafic and ultramafic rocks, often found in lava and in peridotite xenoliths of the mantle, which lava carries to the surface; however, gem-quality peridot occurs in only a fraction of these settings. Peridots can also be found in meteorites.
Peridots can be differentiated by size and composition. A peridot formed as a result of volcanic activity tends to contain higher concentrations of lithium, nickel and zinc than those found in meteorites.[4]
Olivine is an abundant mineral, but gem-quality peridot is rather rare due to its chemical instability on Earth's surface. Olivine is usually found as small grains and tends to exist in a heavily weathered state, unsuitable for decorative use. Large crystals of forsterite, the variety most often used to cut peridot gems, are rare; as a result olivine is considered to be precious.
In the ancient world, mining of peridot, called topazios then, on St. John's Island in the Red Sea began about 300 B.C.[5]
The principal source of peridot olivine today is the San Carlos Apache Indian Reservation in Arizona.[6] It is also mined at another location in Arizona, and in Arkansas, Hawaii, Nevada, and New Mexico at Kilbourne Hole, in the US; and in Australia, Brazil, China, Egypt, Kenya, Mexico, Myanmar (Burma), Norway, Pakistan, Saudi Arabia, South Africa, Sri Lanka, and Tanzania.
In meteorites
Pallasite meteorite with olive-green peridot crystals, found in Fukang, China.
Peridot crystals have been collected from some pallasite meteorites.
Gemology
Peridot is sometimes mistaken for emeralds and other green gems. Notable gemologist George Frederick Kunz[7] discussed the confusion between emeralds and peridots in many church treasures, notably the "Three Magi" treasure in the Dom of Cologne, Germany.
The largest cut peridot olivine is a 310 carat (62 g) specimen in the Smithsonian Museum in Washington, D.C.
Peridot olivine is the birthstone for the month of August.[8]
Gallery
![](https://s2.save4k.ru/pic/8tj6qhgmzK8/mqdefault.jpg)