Weeksite is a distinctive radioactive uranium mineral typically found as radiating clusters of yellow, fan-shaped crystals or crusts. It is highly prized by collectors of radioactive species for its vibrant yellow-green fluorescence under ultraviolet light.

Hardness

Mohs

Luster

Pearly

Streak

Yellow

Transparency

Translucent

mineralrareUranyl silicate group family

Weeksite

Hardness: 2
Luster: Pearly
Streak: Yellow
Transparency: Translucent

Is this weeksite?

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 weeksite with a known reference. Weeksite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Weeksite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Weeksite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: yellow, pale yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: radiating globular aggregates, crusts, fan-shaped sprays.

Often confused with

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

mineral

Boltwoodite

Mohs 3.5

How to tell apart: Boltwoodite is the harder of the two (Mohs 3.5 vs. 2).

How to tell apart: Soddyite is the harder of the two (Mohs 3.5 vs. 2); luster reads pearly on Weeksite and vitreous on Soddyite.

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Often found alongside weeksite

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

All properties

Chemical formula: K₂(UO₂)₂(Si₂O₅)₃·4H₂O
Mohs hardness: 2
Density: 3.9-4.1 g/cm³
Colors: Yellow Pale Yellow
Streak: Yellow
Luster: Pearly
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Radiating Globular Aggregates, Crusts, Fan-shaped Sprays
Cleavage: Perfect
Fluorescence: Bright Yellow-green Under UV
Rarity: Rare
Uses: Collector, Scientific Research
Host rock: Rhyolitic Volcanic Rocks, Hydrothermal Veins
Typical price: $30-200 depending on specimen size and radioactivity levels

Where rockhounds find weeksite

Classic worldwide localities

Thomas Range, Utah, USA
Wheeler County, Georgia, USA
Kazakhstan

Field-hunting tip

Look in rhyolitic volcanic rocks, hydrothermal veins country, the host setting where weeksite typically forms. If you start seeing fluorite, quartz, chalcedony in float, you are in the right ground. Field specimens usually show a radiating globular aggregates, crusts, fan-shaped sprays habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify weeksite?+

Mohs hardness is 2. It typically shows a pearly luster. The streak is yellow. Common colors include yellow, pale yellow.

Where is weeksite found?+

Notable localities include Thomas Range, Utah, USA; Wheeler County, Georgia, USA; Kazakhstan.

How much is weeksite worth?+

Typical asking prices fall in the range of $30-200 depending on specimen size and radioactivity levels. Quality, size, and provenance can move individual specimens well outside that range.

Is weeksite safe to handle?+

This mineral is radioactive. It contains toxic constituents. Contains uranium; radioactive and chemically toxic if ingested or inhaled as dust. Handle with care, wear gloves, and store in a sealed container away from living areas. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like weeksite?+

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

What minerals are found with weeksite?+

Weeksite commonly co-occurs with Fluorite, Quartz, Chalcedony, Autunite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does weeksite form in?+

Weeksite typically forms in rhyolitic volcanic rocks, hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is weeksite used for?+

Weeksite is used in collector, scientific research.

Find weeksite on the map

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