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, 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.