Ruby
Red corundum, the king of stones in Sanskrit and every trade since.
- Family
- Corundum
- Formula
- Al₂O₃
- Mohs
- 9
- System
- Trigonal
Drag to turn
Science
Ruby is corundum coloured by chromium, which also makes it fluoresce red under daylight, adding glow to the body colour. Burmese ruby forms in marble with little iron and glows most; Thai and Mozambican ruby forms in basalt with more iron and reads darker. Most ruby is heated to improve colour and clarity.
- Mineral
- Corundum (variety)
- Formula
- Al₂O₃
- Crystal system
- Trigonal
- Mohs hardness
- 9
- Specific gravity
- 4.00
- Refractive index
- 1.762 to 1.770
- Lustre
- Vitreous to adamantine
- Colours
- Red, Pinkish red
- Birthstone
- July
Composition
Al₂O₃. Made of Aluminium, Oxygen, with trace Chromium responsible for colour.
Origin
- MyanmarMogok, 'pigeon's blood'
- MozambiqueMontepuez
- Thailand
- Sri Lanka
- Madagascar
- Tanzania
- VietnamLuc Yen
Filled dots are primary sources
Rarity
Fine untreated rubies over a few carats are among the rarest of all gems and out-price diamonds of the same weight.
- 1 Abundant
- 2 Common
- 3 Uncommon
- 4 Rare
- 5 Exceptional
Hardness
Ruby sits at 9 on the Mohs scale. It will scratch glass and holds a polish in daily wear.
Energy
Associations from crystal-healing tradition, recorded here as folklore. They are not medical claims.
Chakras
- Root
- Heart
Element
- Fire
Zodiac
- Leo
- Cancer
- Scorpio
- Sagittarius
Planets
- Sun
- Mars
Properties
- Passion
- Vitality
- Courage
- Protection
- Prosperity
Lore
Sanskrit texts call it ratnaraj, king of gems. Burmese warriors inserted rubies under the skin to become invulnerable. Many 'rubies' of European crowns are red spinel, which was not distinguished until the 1780s.
The Sunrise Ruby, 25.59 carats from Mogok, sold for over thirty million dollars in 2015, the highest per-carat price for any coloured stone at that time.
- FluorescenceChromium makes ruby glow red in UV and in daylight.
- Star rubyRutile needles produce a six-rayed star in cabochons.