Andradite (Ca₃Fe₂(SiO₄)₃) is the calcium-iron end-member of the garnet group and the parent of one of the most prized gem garnet varieties — demantoid, the brilliant emerald-green chromium-bearing variant from Russia and Madagascar. Andradite’s strong dispersion gives demantoid a fire that exceeds diamond, making it the most valuable garnet. Black “melanite” (titanium-rich) andradite is a classic skarn species; topazolite (yellow) is rarer collector material.
Key Facts
- Mohs hardness 6.5–7.
- Isometric (cubic); classic dodecahedral and trapezohedral crystals.
- Specific gravity 3.9 — densest of the common garnet species.
- Color varieties: demantoid (green Cr), melanite (black Ti), topazolite (yellow), brownish-red (typical).
- Forms a continuous solid solution series with grossular (Ca-Al) within the ugrandite garnet sub-group.
Notable Localities
Bobrovka (Ural Mountains, Russia) is the classic demantoid locality. Antetezambato (Madagascar) supplies modern gem demantoid. Sichuan skarn deposits and Yunnan host minor Chinese occurrences.
Found at these Localities
- Broken Hill (布罗肯希尔铅锌银矿)
- Franklin and Sterling Hill (富兰克林矿(新泽西))
- Yunnan (云南)
- Sichuan (四川)
