Andradite is the calcium-iron member of the garnet group, famous for its distinct crystal forms and sometimes high luster. Collectors often seek out the brilliant green variety known as Demantoid or the glossy black variety called Melanite. It is most commonly found as a contact metamorphic mineral in skarns and limestone deposits.
Is this andradite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch andradite with a known reference. Andradite sits at Mohs 6.5-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine to resinous, dull.
- 4Match the color rangeCompare against the expected color range: black, brown, green, yellow, red, yellowish brown, greenish yellow, gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: crystalline, euhedral crystals, massive.
Often confused with
Andradite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads adamantine to resinous, dull on Andradite and vitreous to resinous on Schorl.
How to tell apart: Luster reads adamantine to resinous, dull on Andradite and vitreous on Spessartine.
How to tell apart: Luster reads adamantine to resinous, dull on Andradite and vitreous to resinous on Grossular.
Often found alongside andradite
Minerals reported to co-occur with andradite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃Fe₂Si₃O₁₂
- Mohs hardness
- 6.5-7
- Density
- 3.8-3.9 g/cm³
- Streak
- White
- Luster
- Adamantine to resinous, dull
- Transparency
- Transparent to translucent
- Crystal system
- Cubic
- Crystal habit
- Crystalline, euhedral crystals, massive
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Gemstone
- Host rock
- In skarns from contact metamorphosed impure limestones or calcic igneous rocks; in chlorite schists and serpentinites; in alkalic igneous rocks, then typically titaniferous
Where rockhounds find andradite
3 mapped spotsClassic worldwide localities
- Stanley Butte, Graham Co., Arizona, USA
- Garnet Hill, Calaveras Co., and around the Gem mine, San Benito Co., California, USA
- Franklin and Sterling Hill, Sussex Co., New Jersey, USA
- Magnet Cove, Hot Spring Co., Arkansas, USA
- Italy, at Frascati, Alban Hills, Lazio
- Val Malenco, Lombardy
Field-hunting tip
Where it forms: In skarns from contact metamorphosed impure limestones or calcic igneous rocks; in chlorite schists and serpentinites; in alkalic igneous rocks, then typically titaniferous. If you start seeing vesuvianite, chlorite, epidote in float, you are in the right ground. Typical habit: crystalline, euhedral crystals, massive. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Mexico, Pennsylvania, Utah. Start trip planning there.
Common questions
How do you identify andradite?+
Where is andradite found?+
Can I find andradite in the United States?+
What rocks look like andradite?+
What minerals are found with andradite?+
What kind of rock does andradite form in?+
What is andradite used for?+
Find andradite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
