Tyretskite is a rare borate mineral typically found in sedimentary salt sequences and evaporite basins. Collectors should look for its tabular monoclinic crystals in saline beds, often associated with other borate species and evaporite minerals.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareBorate family

Tyretskite

Hardness: 5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this tyretskite?

5-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 tyretskite with a known reference. Tyretskite sits at Mohs 5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: white, brownish, brownish white.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals, massive.

Often confused with

Tyretskite vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside tyretskite

Minerals reported to co-occur with tyretskite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Ca₂B₅O₉(OH)·H₂O
Mohs hardness: 5
Density: 2.189 g/cm³
Colors: White Brownish Brownish white
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Tabular crystals, massive
Cleavage: Good
Rarity: Rare
Uses: Collector
Host rock: Cavity in dolomitic saline rock, in drillcore from a depth of 1233 m

Where rockhounds find tyretskite

Classic worldwide localities

Tyret railway station, on the east Siberian railway, in the Lena-Angara salt basin, Irkutsk district, Siberia, Russia (type locality)

Field-hunting tip

Where it forms: Cavity in dolomitic saline rock, in drillcore from a depth of 1233 m. If you start seeing halite, gypum, anhydrite 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 tyretskite?+

Mohs hardness is 5. Luster: vitreous. The streak is white. Common colors include white, brownish, brownish white.

Where is tyretskite found?+

Notable localities include Tyret railway station, on the east Siberian railway, in the Lena-Angara salt basin, Irkutsk district, Siberia, Russia (type locality).

What rocks look like tyretskite?+

Tyretskite is most often confused with Colemanite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with tyretskite?+

Tyretskite commonly co-occurs with Halite, Gypum, Anhydrite, Magnesite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tyretskite form in?+

Where it forms: Cavity in dolomitic saline rock, in drillcore from a depth of 1233 m. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tyretskite used for?+

Tyretskite is used in collector.

Find tyretskite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.