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 bluish greenish streak and association with skarn minerals like magnetite and calcite.

Hardness

7.5

Mohs

Luster

Vitreous

Transparency

Transparent to translucent

mineralrare

Tashelgite

Hardness: 7.5
Luster: Vitreous
Transparency: Transparent to translucent

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Is this tashelgite?

4-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch tashelgite with a known reference. Tashelgite sits at Mohs 7.5, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
3
Match the color range
Compare against the expected color range: bluish green.
4
Look at form & habit
Crystal 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: Tashelgite is noticeably harder (Mohs 7.5 vs. 5.5-6.5); luster reads vitreous on Tashelgite and metallic to submetallic, may be dull on Magnetite.

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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: CaMgFeAl₉O₁₆(OH)
Mohs hardness: 7.5
Density: 3.67 g/cm³
Colors: Bluish green
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Monoclinic
Crystal habit: Tabular crystals, massive
Cleavage: None
Rarity: Rare
Uses: Collector, Scientific research
Host rock: In skarn-like rocks anomalously enriched with Al2O3

Where rockhounds find tashelgite

Classic worldwide localities

Tashelginskoye iron deposit, Gornaya Shoriya, Russia

Field-hunting tip

Where it forms: In skarn-like rocks anomalously enriched with Al2O3. If you start seeing calcite, hibonite, grossular in float, you are in the right ground. Typical habit: tabular crystals, massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tashelgite?+

Mohs hardness is 7.5. Luster: vitreous. Common colors include bluish green.

Where is tashelgite found?+

Notable localities include Tashelginskoye iron deposit, Gornaya Shoriya, Russia.

What rocks look like tashelgite?+

Tashelgite is most often confused with Spinel, Magnetite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with tashelgite?+

Tashelgite commonly co-occurs with Calcite, Hibonite, Grossular, Vesuvianite, Hercynite, Magnetite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tashelgite form in?+

Where it forms: In skarn-like rocks anomalously enriched with Al2O3. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tashelgite used for?+

Tashelgite is used in collector, scientific research.

Find tashelgite on the map

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