Kummerite is an extremely rare, purplish-pink variety of corundum specifically associated with the Franklin mining district in New Jersey. Collectors prize it for its unique locality-based color characteristics and its status as one of the few corundum occurrences in a metamorphosed zinc-iron-manganese deposit.
Is this kummerite?
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 kummerite with a known reference. Kummerite sits at Mohs 9 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Kummerite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Kummerite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: pink, violet, lavender.
- 5Look at form & habitCrystal system: trigonal. Typical habit: prismatic crystals.
Often confused with
Kummerite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside kummerite
Minerals reported to co-occur with kummerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₂O₃
- Mohs hardness
- 9
- Density
- 4.0 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Prismatic Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Gemstone, Collector
- Host rock
- Metamorphic Rocks
- Typical price
- $100-500 per carat
Where rockhounds find kummerite
Classic worldwide localities
- Franklin, New Jersey, USA
Field-hunting tip
Look in metamorphic rocks country — that is the host setting where kummerite typically forms. If you start seeing gahnite, calcite, willemite in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kummerite?+
Where is kummerite found?+
How much is kummerite worth?+
What rocks look like kummerite?+
What minerals are found with kummerite?+
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Find kummerite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
