Mopungite is a rare secondary mineral typically occurring in the oxidized zones of antimony deposits. It is best identified by its colorless to white tetragonal bipyramidal crystals, usually found associated with other antimony oxidation products like stibiconite.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent to translucent

mineralrare

Mopungite

Hardness: 3
Luster: Vitreous
Streak: White
Transparency: Transparent to translucent

Is this mopungite?

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 mopungite with a known reference. Mopungite sits at Mohs 3, 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: vitreous.
4
Match the color range
Compare against the expected color range: colorless, milky white.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: encrustations, pseudo cubic, pseudomorphous.

Often confused with

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

mineral

Stibiconite

Mohs 5.5-7

How to tell apart: Stibiconite is the harder of the two (Mohs 5.5-7 vs. 3); streak differs, so Mopungite leaves white, Stibiconite leaves light yellow; luster reads vitreous on Mopungite and pearly, opaline, glassy to earthy on Stibiconite.

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Often found alongside mopungite

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

All properties

Chemical formula: NaSb(OH)₆
Mohs hardness: 3
Density: 3.21 g/cm³
Colors: Colorless Milky white
Streak: White
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Tetragonal
Crystal habit: Encrustations, pseudo cubic, pseudomorphous
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: An oxidation product of stibnite

Where rockhounds find mopungite

Classic worldwide localities

Green prospect, Mopung Hills, Lake district, Churchill Co., Nevada, USA
Cetine mine, 20 km southwest of Siena, Tuscany, Italy

Field-hunting tip

Where it forms: An oxidation product of stibnite. If you start seeing selenium, sulfur, stibiconite in float, you are in the right ground. Typical habit: encrustations, pseudo cubic, pseudomorphous. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify mopungite?+

Mohs hardness is 3. Luster: vitreous. The streak is white. Common colors include colorless, milky white.

Where is mopungite found?+

Notable localities include Green prospect, Mopung Hills, Lake district, Churchill Co., Nevada, USA; Cetine mine, 20 km southwest of Siena, Tuscany, Italy.

Is mopungite safe to handle?+

Mopungite contains antimony. Contains antimony, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust when breaking or cleaning specimens.

What rocks look like mopungite?+

Mopungite is most often confused with Stibiconite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with mopungite?+

Mopungite commonly co-occurs with Selenium, Sulfur, Stibiconite, Sénarmontite, Roméite, Tripuhyite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does mopungite form in?+

Where it forms: An oxidation product of stibnite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is mopungite used for?+

Mopungite is used in collector.

Find mopungite on the map

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