Mohs · 1812 · ten reference minerals
Friedrich Mohs put ten minerals in the order they scratch one another. Corundum is 9, diamond is 10, and the step between them is larger than the eight steps beneath.
Photo: Jorge Romero / Pexels
A reference on gem minerals, the mines they come from, the people who cut them and the named stones with a documented record.
Three of the eight sections
Corundum
Ruby and sapphire are the same mineral — corundum — and what separates them is a fraction of a percent of chromium, iron or titanium.
Named Stones
Famous individual stones — the Hope Diamond, the Koh-i-Noor, the Cullinan, the Black Prince's Ruby — each with a verified provenance and a documented history.
Cutting
From rose cut to Tolkowsky's 1919 brilliant, from cabochon to step cut — the history of how gem material is shaped, and the trade centres where the work is done.
The flagship piece · Named Stones
Harry Winston posted it from New York in November 1958, insured for a million dollars, and the postage came to $2.44. Trace boron makes the blue — and makes the stone glow red for twenty seconds after ultraviolet light.
The Drawer
Tray 01
MgAl₂O₄, separated from corundum in 1783 and still called ruby for a century after.
Tray 02
Hydrated silica; the body colour belongs to the host dirt, not the stone.
Tray 03
Two minerals — jadeite and nephrite — separated mineralogically in 1863.
Tray 04
Lazurite with calcite and pyrite, ground for ultramarine before it was a gem.
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