Metahaiweeite is a rare secondary uranium silicate typically found as yellow, radiating bladed aggregates or thin crusts in sedimentary deposits. It is best identified by its strong green fluorescence under ultraviolet light and its close association with silica-rich lake beds.

Hardness

2-3

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrareHaiweeite Group family

Metahaiweeite

Hardness: 2-3
Luster: Pearly
Streak: White
Transparency: Translucent

No image

Is this metahaiweeite?

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

Often confused with

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

mineral

Haiweeite

Mohs 1

How to tell apart: Metahaiweeite is noticeably harder (Mohs 2-3 vs. 1).

How to tell apart: Streak differs — Metahaiweeite leaves white, Autunite leaves pale yellow.

How to tell apart: Streak differs — Metahaiweeite leaves white, Meta-autunite leaves yellow.

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Often found alongside metahaiweeite

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

All properties

Chemical formula: Ca(UO₂)₂(Si₂O₅)₂·nH₂O
Mohs hardness: 2-3
Density: 2.8 g/cm³
Colors: Yellow Pale Yellow White
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Radiating Aggregates, Platy Crystals, Crusts
Cleavage: Perfect
Fluorescence: Bright Green Under SW UV
Rarity: Rare
Uses: Collector
Host rock: Sedimentary Lake Beds
Typical price: $20-150 thumbnail

Where rockhounds find metahaiweeite

Classic worldwide localities

Coso Mountains, California, USA
Haiwee Reservoir, California, USA
Utah, USA

Field-hunting tip

Look in sedimentary lake beds country — that is the host setting where metahaiweeite typically forms. If you start seeing opal, quartz, uranophane in float, you are in the right ground. Field specimens usually show a radiating aggregates, platy crystals, crusts habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify metahaiweeite?+

Mohs hardness is 2-3. It typically shows a pearly luster. The streak is white. Common colors include yellow, pale yellow, white.

Where is metahaiweeite found?+

Notable localities include Coso Mountains, California, USA; Haiwee Reservoir, California, USA; Utah, USA.

How much is metahaiweeite worth?+

Typical asking prices fall in the range of $20-150 thumbnail. Quality, size, and provenance can move individual specimens well outside that range.

Is metahaiweeite safe to handle?+

This mineral is radioactive. It contains toxic constituents. This mineral contains uranium and is radioactive; handle with care, use appropriate storage containers, and avoid inhalation of dust or ingestion. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like metahaiweeite?+

Metahaiweeite is most often confused with Haiweeite, Autunite, Meta-autunite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with metahaiweeite?+

Metahaiweeite commonly co-occurs with Opal, Quartz, Uranophane. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does metahaiweeite form in?+

Metahaiweeite typically forms in sedimentary lake beds. Working float back to the host body is the standard way to chase a fresh occurrence.

What is metahaiweeite used for?+

Metahaiweeite is used in collector.

Find metahaiweeite on the map

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