Birthstone
Ruby
Usually described as red.
- Colour
- red
- Month
- July
- Status
- 1912 and todayOn the list adopted in 1912, as a birth-stone, and still on today's. The two lists compared.
Name and history
The name comes from Old French rubi and the Medieval Latin rubinus lapis, red stone, from the Latin rubeus, red, which is related to ruber and goes back to an ancient root meaning red or ruddy.
What it actually is
| Species | Corundum |
|---|---|
| Composition | Al₂O₃ |
| Crystal system | trigonal |
| Hardness | 9 on the Mohs scale. Harder than anything it is likely to meet. |
| Cleavage | none; parting in up to three directions |
| What makes the colour | chromium (Cr³⁺) replacing aluminium — the same element that colours emerald green colours corundum red, and the more chromium, the stronger the red; iron present with it pushes the colour towards a darker, browner red |
| Mined in | Mozambique, Myanmar, Madagascar, Tanzania, Sri Lanka |
Hardness, composition and crystal system are standard mineralogical values. Where published sources disagree, the range given covers them.
How it gets damaged
Second only to diamond in hardness and excellent for daily wear, but parting planes make it brittle under a hard blow; lead-glass-filled stones are far more fragile and are damaged by ultrasonic cleaners, a jeweller's torch and even household acids such as lemon juice.
What is routinely done to it
Heating to as much as 1,800 °C is routine and permanent; separately, a great deal of low-grade material is filled with high-lead glass, which is neither stable nor comparable in value and must be disclosed.
This describes the physical stone. Nothing on this site claims a gemstone has any therapeutic or healing effect — see the disclaimer.
Which list it is on
| Month | The 1912 list | Today's list |
|---|---|---|
| July | Birth-stone | Yes |