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

3.5

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrareHaiweeite Group family

Metahaiweeite

Hardness: 3.5
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 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: pearly.
4
Match the color range
Compare against the expected color range: greenish yellow, light yellow.
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.

How to tell apart: Metahaiweeite is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs, so Metahaiweeite leaves white, Autunite leaves pale yellow; luster reads pearly on Metahaiweeite and vitreous, pearly on {001} on Autunite.

How to tell apart: Metahaiweeite is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs, so 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: 3.5
Density: 3.35 g/cm³
Colors: Greenish yellow Light yellow
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Radiating aggregates, platy crystals, crusts
Cleavage: Distinct on {100}
Fluorescence: Dull green under SW and LW UV
Rarity: Rare
Uses: Collector
Host rock: sedimentary lake beds

Where rockhounds find metahaiweeite

Classic worldwide localities

Haiwee Reservoir, Inyo County, California, USA (type locality)

Field-hunting tip

Where it forms: sedimentary lake beds. If you start seeing opal, quartz, uranophane in float, you are in the right ground. Typical habit: radiating aggregates, platy crystals, crusts. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify metahaiweeite?+

Mohs hardness is 3.5. Luster: pearly. The streak is white. Common colors include greenish yellow, light yellow.

Where is metahaiweeite found?+

Notable localities include Haiwee Reservoir, Inyo County, California, USA (type locality).

Is metahaiweeite safe to handle?+

Metahaiweeite contains uranium or thorium and calls for real care. This mineral contains uranium and is radioactive; handle with care, use appropriate storage containers, and avoid inhalation of dust or ingestion.

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?+

Where it forms: 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.