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

mineralrare

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, 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.