The Nivoda Gemstone Encyclopedia

The World's
Gemstone Vault,
On Demand.

From rough to cut - the history, science, treatments and care of every gemstone traded on the Nivoda marketplace.

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Logan Sapphire — 422.99-carat Ceylon sapphire and diamond brooch

Photo: Chip Clark, Smithsonian National Museum of Natural History

Featured

The Big Four

All gems

No. 01

Sapphire

Mohs 9

Corundum in every colour but red.

No. 02

Ruby

Mohs 9

The king of gems - corundum coloured by chromium.

No. 03

Emerald

Mohs 7.5–8

Beryl coloured by chromium and vanadium - the green of empires.

No. 04

Tourmaline

Mohs 7–7.5

The most colour-diverse gem species on Earth.

Rough alexandrite crystal alongside a faceted alexandrite showing its dramatic color change

Photo courtesy of Omi

From the rough · June

One gemstone, two colours - by day and by candlelight.

Alexandrite is chrysoberyl's rarest face - bluish-green in daylight, raspberry-red under incandescent light. First unearthed in the Ural Mountains in 1830 and named for the future Tsar Alexander II, fine material now comes from Brazil, Sri Lanka, and East Africa - in carats counted, not kilos.

Read the alexandrite entry

June · Birthstone of the month

This Month's
Gemstones.

All twelve months

Members only

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The World'sGemstone Vault,On Demand.