Wattersite is a rare mercury-chromium mineral characterized by its vibrant red color and high density. It is typically found in mercury-rich hydrothermal deposits within serpentinized rocks, appearing as small, distinct tabular crystals.

Hardness

Mohs

Luster

Submetallic

Streak

Dark brick-red

Transparency

Opaque, translucent on thin edges

mineralrare

Wattersite

Hardness: <5
Luster: Submetallic
Streak: Dark brick-red
Transparency: Opaque, translucent on thin edges

Is this wattersite?

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 wattersite with a known reference. Wattersite sits at Mohs <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: dark brick-red.
3
Read the luster
Hold the specimen under a strong light. Luster: submetallic.
4
Match the color range
Compare against the expected color range: bronze, reddish brown, black.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: crystalline, encrustations.

Often confused with

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

mineral

Cinnabar

Mohs 2-2.5

How to tell apart: Wattersite is noticeably harder (Mohs <5 vs. 2-2.5); streak differs, so Wattersite leaves dark brick-red, Cinnabar leaves scarlet; luster reads submetallic on Wattersite and adamantine, inclining to metallic when dark; dull in friable material on Cinnabar.

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Often found alongside wattersite

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

All properties

Chemical formula: Hg³⁺₄Hg²⁺CrO₆
Mohs hardness: <5
Density: 8.91 g/cm³
Colors: Bronze Reddish brown Black
Streak: Dark brick-red
Luster: Submetallic
Transparency: Opaque, translucent on thin edges
Crystal system: Monoclinic
Crystal habit: Crystalline, encrustations
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: A rare mineral in a mercury deposit in silicate–carbonate rock hydrothermally altered from serpentinite

Where rockhounds find wattersite

Classic worldwide localities

Clear Creek mercury mine, new Idria district, San Benito County, California (type locality)

Field-hunting tip

Where it forms: A rare mineral in a mercury deposit in silicate–carbonate rock hydrothermally altered from serpentinite. If you start seeing cinnabar, mercury in float, you are in the right ground. Typical habit: crystalline, encrustations. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify wattersite?+

Mohs hardness is <5. Luster: submetallic. The streak is dark brick-red. Common colors include bronze, reddish brown, black.

Where is wattersite found?+

Notable localities include Clear Creek mercury mine, new Idria district, San Benito County, California (type locality).

Is wattersite safe to handle?+

Wattersite contains hexavalent chromium and mercury and calls for real care. Contains mercury and chromium; toxic if ingested, inhaled as dust, or handled excessively. Wash hands thoroughly after handling and keep in a sealed container.

What rocks look like wattersite?+

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

What minerals are found with wattersite?+

Wattersite commonly co-occurs with Cinnabar, Mercury. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does wattersite form in?+

Where it forms: A rare mineral in a mercury deposit in silicate–carbonate rock hydrothermally altered from serpentinite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is wattersite used for?+

Wattersite is used in collector.

Find wattersite on the map

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