Properties
| Category | Oxide minerals |
|---|---|
| Formula | Aluminum oxide with chromium, Al2O3:Cr |
| Crystal system | Trigonal |
| Color | Orangy red through strongly purplish red. |
| Crystal habit | Terminated tabular hexagonal prisms |
| Cleavage | No true cleavage |
| Fracture | Conchoidal, splintery |
| Tenacity | Brittle |
| Mohs scale hardness | 9.0 |
| Luster | Subadamantine, vitreous, pearly (on partings) |
| Streak | White |
| Diaphaneity | Transparent, translucent |
| Specific gravity | 3.97–4.05 |
From the Wikipedia article
Ruby is a pinkish-red to blood-red-colored gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires, and rubies are also sometimes referred to as "red sapphires".
Source
Source record: crystal-compendium/ruby/minerals.json. Fetched from English Wikipedia by the operator 2 October 2026.
https://en.wikipedia.org/wiki/Ruby — revision id 1377290699. Text and properties from Wikipedia, licensed CC BY-SA 4.0.