Tashelgite is an extremely rare aluminate mineral first discovered in the iron-ore skarns of the Tashelginskoye deposit in Russia. It typically occurs as small tabular crystals or massive aggregates and is distinguished by its characteristic brownish streak and association with skarn minerals like magnetite and calcite.
Is this tashelgite?
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 tashelgite with a known reference. Tashelgite sits at Mohs 5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Tashelgite leaves a brown streak.
- 3Read the lusterHold the specimen under a strong light. Tashelgite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark brown, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, massive.
Often confused with
Tashelgite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Spinel is the harder of the two (Mohs 8 vs. 5-6); streak differs — Tashelgite leaves brown, Spinel leaves white.
How to tell apart: Streak differs — Tashelgite leaves brown, Magnetite leaves black; luster reads vitreous on Tashelgite and metallic on Magnetite.
Often found alongside tashelgite
Minerals reported to co-occur with tashelgite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaMgAl₉O₁₅(OH)
- Mohs hardness
- 5-6
- Density
- 3.37 g/cm³
- Colors
- Streak
- Brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Massive
- Cleavage
- None Observed
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Skarn Deposits
- Typical price
- $50-500 depending on specimen quality and rarity
Where rockhounds find tashelgite
Classic worldwide localities
- Tashelginskoye iron deposit, Gornaya Shoriya, Russia
Field-hunting tip
Look in skarn deposits country — that is the host setting where tashelgite typically forms. If you start seeing magnetite, calcite, serpentine in float, you are in the right ground. Field specimens usually show a tabular crystals, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find tashelgite on the map
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