Rumseyite is a very rare lead oxyhalide mineral first discovered in the Big Bunch mine in Arizona. It typically occurs as tiny, tabular, colorless to white crystals within oxidized lead-bearing veins and is highly prized by micromount collectors.

Hardness

Mohs

Luster

Adamantine

Streak

White

Transparency

Transparent

mineralrare

Rumseyite

Hardness: 2
Luster: Adamantine
Streak: White
Transparency: Transparent

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Is this rumseyite?

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 rumseyite with a known reference. Rumseyite 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. Rumseyite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Rumseyite typically shows a adamantine luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: tabular crystals.

Often confused with

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

How to tell apart: Laurionite is the harder of the two (Mohs 3-3.5 vs. 2).

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Often found alongside rumseyite

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

All properties

Chemical formula: Pb₂OFCl
Mohs hardness: 2
Density: 7.52 g/cm³
Colors: Colorless White
Streak: White
Luster: Adamantine
Transparency: Transparent
Crystal system: Tetragonal
Crystal habit: Tabular Crystals
Cleavage: Perfect On {001}
Rarity: Rare
Uses: Collector
Host rock: Oxidized Lead Deposits
Typical price: $100-500 per specimen

Where rockhounds find rumseyite

Classic worldwide localities

Big Bunch claim, Arizona, USA

Field-hunting tip

Look in oxidized lead deposits country — that is the host setting where rumseyite typically forms. If you start seeing galena, anglesite, cerussite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify rumseyite?+

Mohs hardness is 2. It typically shows a adamantine luster. The streak is white. Common colors include colorless, white.

Where is rumseyite found?+

Notable localities include Big Bunch claim, Arizona, USA.

How much is rumseyite 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.

Is rumseyite safe to handle?+

It contains toxic constituents. Contains lead, which is toxic if ingested or inhaled as dust; wash hands thoroughly after handling. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like rumseyite?+

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

What minerals are found with rumseyite?+

Rumseyite commonly co-occurs with Galena, Anglesite, Cerussite, Phosgenite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does rumseyite form in?+

Rumseyite typically forms in oxidized lead deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is rumseyite used for?+

Rumseyite is used in collector.

Find rumseyite on the map

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