silicates
Pyrope
Mg3Al2(SiO4)3
- Also known as
- Bohemian garnetCape ruby
- Crystal system
- cubic
- Hardness
- 7–7.5 on the Mohs scale
- Lustre
- vitreous
- Colour
- Blood red to purplish red
- Where it forms
- At high pressure, in peridotite and in kimberlite — the rock that carries diamonds up from the mantle. Pyrope is a mantle mineral brought to the surface.
- Chiefly from
- Bohemia, Czech RepublicSouth AfricaArizona, United States
Why it is that colour
Iron and chromium impurities; pure pyrope would be colourless. The name is from the Greek for fiery-eyed.
Safety
Safe to handle.
Where it comes from
Bohemian garnet has been worked since the sixteenth century and remains a protected designation in the Czech Republic. Much material sold as Bohemian garnet is not.
Historical use
Bohemian garnet jewellery — dense clusters of small deep-red stones in gold — was a major nineteenth-century industry. Pyrope is also a diamond indicator mineral, and prospectors look for it in stream sediments as a sign that a kimberlite pipe is upstream.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
Shares the general garnet tradition; not distinguished as a species until the nineteenth century, so it has no separate ancient attribution.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Worth knowing
Pyrope is one of the minerals that finds diamonds. It forms at mantle depths and is carried up in kimberlite, and unlike diamond it is common and conspicuous. Diamond exploration therefore proceeds by sampling stream sediments for pyrope and a handful of other indicator minerals, then walking upstream until the trail stops. Most of the world's diamond mines were found this way.
A particular chromium-rich, calcium-poor pyrope — called G10 — is the strongest indicator, because it forms in the same narrow window of pressure and temperature where diamond is stable.
Identity checked against IMA-CNMNC master list, June 2025.