What is Pyrope?
Pyrope is the magnesium-rich red garnet, valued as a durable gemstone and as a geochemical indicator of mantle and ultramafic rocks.
Mineralogy and crystal structure
Reference formula: Mg3Al2Si3O12. Pyrope is a cubic garnet end member, but natural crystals commonly contain almandine, grossular or chromium substitutions. Gem colour depends on chemistry and inclusions. Pyrope is classified with silicates and has a cubic crystal system. Typical hardness is 7–7.5 on the Mohs scale and specific gravity is approximately 3.5–3.7.
Colour, lustre and habit
Typical colours include deep red, purple-red, red-brown, pink. The usual dodecahedral, granular, massive habit and vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Pyrope forms in or is associated with mantle-derived peridotites, kimberlites, high-pressure metamorphic rocks and alluvial deposits. Important documented localities include Czech Republic, South Africa, Tanzania, Mozambique, the United States and Canada.
The deep red garnet of the mantle
Pyrope gives the familiar red garnet a geological depth: crystals can travel from the mantle in kimberlite and survive as durable alluvial gems.
Collecting and care
Protect polished stones from strong impact and extreme heat; clean with mild soapy water and avoid ultrasonic treatment when fractured.
