Sosedkoite is an exceptionally rare potassium-aluminum-tantalum oxide mineral found in complex granite pegmatites. It typically occurs as small, distinct yellow-orange tabular crystals associated with other rare tantalum species.

Hardness

3.5

Mohs

Luster

Vitreous

Streak

Yellow

Transparency

Translucent

mineralrarenull family

Sosedkoite

Hardness: 3.5
Luster: Vitreous
Streak: Yellow
Transparency: Translucent

Is this sosedkoite?

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 sosedkoite with a known reference. Sosedkoite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Sosedkoite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Sosedkoite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, yellowish-orange.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals, platy.

Often found alongside sosedkoite

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

All properties

Chemical formula: (K,Na)₅Al₄(Ta,Nb,W)₁₀O₃₀
Mohs hardness: 3.5
Density: 3.84 g/cm³
Colors: Yellow Yellowish-orange
Streak: Yellow
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Tabular Crystals, Platy
Cleavage: Good
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $100-500 per specimen

Where rockhounds find sosedkoite

Classic worldwide localities

Dzhan-Taga deposit, Tajikistan
Pamir Mountains, Tajikistan

Field-hunting tip

Look in granite pegmatites country — that is the host setting where sosedkoite typically forms. If you start seeing muscovite, quartz, albite in float, you are in the right ground. Field specimens usually show a tabular crystals, platy habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify sosedkoite?+

Mohs hardness is 3.5. It typically shows a vitreous luster. The streak is yellow. Common colors include yellow, yellowish-orange.

Where is sosedkoite found?+

Notable localities include Dzhan-Taga deposit, Tajikistan; Pamir Mountains, Tajikistan.

How much is sosedkoite worth?+

Typical asking prices fall in the range of $100-500 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What minerals are found with sosedkoite?+

Sosedkoite commonly co-occurs with muscovite, quartz, albite, columbite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does sosedkoite form in?+

Sosedkoite typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is sosedkoite used for?+

Sosedkoite is used in collector.

Find sosedkoite on the map

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