Peridot
Peridot is an olive green gemstone that (understandably) is often called olivine, as it relates to the gemstone colour. Whereas olivine is actually the name of a group of minerals, of which fosterite is a species and peridot is a variety of that species.
It is one of the few gemstones that occurs in one base colour, ranging from light yellowish green, to olive green, to dark green.
The origin of the word peridot is uncertain, as there is more than one claimant. For example, it is believed to have come from either:
The Arabic word faradat meaning 'gem'.
The French word peritot meaning 'unclear' probably in reference to cloudy peridot.
The Greek word peridona meaning 'to give generously, or richly, or plenty'
The Hebrew word pitah from the bible, meaning 'yellow' maybe in association with yellowish peridot.
So the origin can not be determined with any certainty.
Peridots are typically bright with good saturation and often show attractive yellow flashes in faceted stones, due to pleochroism. Inclusions in the form of 'lily pad' shaped stress fractures are characteristic of peridot and when present help identify the stone.
Although material with chatoyancy or asterism is rare, cat's eye peridot and star stones are occasionally produced.
The first source of peridot is believed to be the Red Sea island of Zebirget (Zabargad, St. John’s island) where it was mined over 3,500 years ago. The peridot from Zebirget is of superior quality and although it is still sourced from the island, mining is sporadic.
Source locations for peridot also include:
Australia (Queensland), Brazil ( Minas Gerais), China, Czech Republic, Kenya, Mexico, Myanmar, Norway, Pakistan, South Africa, Sri Lanka, Tanzania and USA (Arizona).
Properties of the Gemstone and Additional Information
| Gemstone type: | A variety of the fosterite species, from the olivine group of minerals. |
| Crystal System: | Orthorhombic |
| Chemical Composition: | Magnesium iron silicate, (Mg,Fe)2SiO4. |
| Colour: | Pale yellow-green to olive green, deep green to brown. |
| Lustre: | Vitreous; may be oily or greasy. |
| Pleochroism: | Weak: typically pale green to yellowish-green. |
| Dispersion: | Medium |
| Hardness: | 6 1/2 on the Mohs' scale |
| Toughness: | Fair: May be damaged by thermal shock. Care is needed not to apply too much pressure when setting. |
| Cleavage: | Indistinct |
| Density in gm/cc: | 3.32 to 3.37 |
| Double refraction: | Yes |
| Refractive index: | 1.65 to 1.69 |
Common Treatments
Peridot is not normally treated