Peridot

Olivine · (Mg,Fe)₂SiO₄. Colors: brown-green to yellowish green to pure green.

Brief us for this stone In the encyclopedia

Mohs: 6.5–7
RI: 1.65–1.69
SG: 3.34
Crystal system: orthorhombic

(Fig. 01)Stone record

Peridot at a glance.

Peridot specimen — Photo: Smithsonian NMNH · CC0

Species: Olivine
Formula: (Mg,Fe)₂SiO₄
Crystal system: orthorhombic
Mohs: 6.5–7
RI: 1.65–1.69
SG: 3.34
Colors: brown-green to yellowish green to pure green

(Fig. 02)In the encyclopedia3

What the encyclopedia says.

3 passages, quoted as published. Each links to the full entry and the sources of its chapter.

02.12 · Stones
Other transparent gems: tanzanite to spodumene
Peridot is gem olivine, colored yellowish green by the iron in its composition, and occurs in basalts, in mantle rocks pushed to the surface and, rarely, in meteorites. Iolite, gem cordierite, is strongly pleochroic. Kunzite is the pink to violetish purple variety of spodumene, LiAlSi₂O₆, colored by manganese and recognized around 1902. Green hiddenite and yellow triphane are the other spodumene varieties.
Read the full entry
03.03 · Science
Specific gravity, refraction and dispersion
Refractive index (RI) expresses how much light slows and bends as it enters a gem: quartz reads about 1.54, corundum 1.762 to 1.770, diamond 2.42. Stones outside the cubic system are doubly refractive, splitting light into two rays with different indices. The difference between them is the birefringence. Peridot’s birefringence of 0.035 to 0.038 is large enough that you can see two of each pavilion facet through the crown.
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05.04 · Mining
Rubies and sapphires in Asia
Rubies and sapphires are both corundum, crystalline aluminum oxide colored by trace elements: chromium makes ruby red, and iron with titanium makes sapphire blue. Mogok, in Myanmar’s Mandalay Region, has supplied fine rubies for centuries, along with sapphire, spinel and peridot, mostly from small pits and hand panning. The town became a front line in Myanmar’s civil war: the Ta’ang National Liberation Army captured it in July 2024 and withdrew after a China-brokered ceasefire in October 2025.
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(Fig. 03)Origins2

Where it is mined.

Localities from the mine map in Chapter 05.

Locality	Country	Status	Note
Mogok	Myanmar	artisanal	The classic ruby district; held by TNLA rebels from July 2024 to October 2025
Zabargad (St John’s Island)	Egypt	historic	Red Sea island 3.2 by 2.4 km, worked for peridot since antiquity; commercial mining ran from about 1906 until nationalisation in 1958