PERIDOT OLIVINE BOMB
A lovely specimen of Peridot in Basalt. Also known as a Peridot Olivine Bomb for the manner in which they are fired out of volcanoes. Olivine is the mineral name for this stone. I personally love the stuff, and this piece is Australian which makes it even better!
Mt Shadwell, Mortlake, Victoria, Australia.
6cm x 6cm x 5cm, 240g.
Peridot (Mg, Fe)2SiO4.
Peridot (pronounced pair-a-doe) is the gem variety of olivine. Olivine is not an official mineral. It is composed of two minerals Fayalite and Forsterite. Fayalite is the iron rich member with a pure formula of Fe2SiO4. Forsterite is the magnesium rich member with a pure formula of Mg2SiO4.
Olivine’s formula is written as (Mg, Fe)2SiO4 to show the substitution of the magnesium and iron. Usually closer to Forsterite than Fayalite in composition although iron is the coloring agent for Peridot. The best colored Peridot has an iron percentage of less than 15% and includes Nickel and Chromium as trace elements that may also contribute to the best Peridot color.
Gem quality Peridot comes from the ancient source of Zagbargad (Zebirget) Island in the Red Sea off the coast of Egypt; Mogok, Myanmar (formerly known as Burma); Kohistan, Pakistan; Minas Gerais, Brazil; Eifel, Germany; Chihuahua, Mexico; Ethiopia; Australia; Peridot Mesa, San Carlos Apache Reservation, Gila County, Arizona and Salt Lake Crater, Oahu, Hawaii, USA. The best quality Peridot has historically come either from Myanmar or Egypt.
New sources in Pakistan are challenging that claim with some exceptional specimens. The Arizona gem material is of lesser quality, but is far more abundant and is therefore much more affordable. An estimated 80 – 95% of all world production of Peridot comes from Arizona. The Myanmar, Pakistani and Egyptian gems are rarer and of better quality and thus quite valuable approaching the per carat values of top gemstones. Possibly the most unusual Peridot is that which comes from iron-nickel meteorites called Pallasites.