Brassite is a rare magnesium arsenate mineral that typically forms as delicate crusts or small tabular crystals in the oxidation zones of arsenic-bearing ore deposits. Due to its solubility and rarity, it is primarily sought after by advanced mineral collectors who specialize in arsenate species.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrare

Brassite

Hardness: 2
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this brassite?

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 brassite with a known reference. Brassite 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. Brassite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Brassite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, yellowish-white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: crusts, tabular crystals.

Often confused with

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

Often found alongside brassite

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

All properties

Chemical formula: MgHAsO₄·4H₂O
Mohs hardness: 2
Density: 2.68 g/cm³
Colors: Yellow Yellowish-white
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Crusts, Tabular Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Oxidized Hydrothermal Arsenic-rich Deposits
Typical price: $50-300 per specimen

Where rockhounds find brassite

Classic worldwide localities

Jáchymov, Czech Republic
Wittichen, Germany

Field-hunting tip

Look in oxidized hydrothermal arsenic-rich deposits country — that is the host setting where brassite typically forms. If you start seeing arsenolite, scorodite in float, you are in the right ground. Field specimens usually show a crusts, tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify brassite?+

Mohs hardness is 2. It typically shows a vitreous luster. The streak is white. Common colors include yellow, yellowish-white.

Where is brassite found?+

Notable localities include Jáchymov, Czech Republic; Wittichen, Germany.

How much is brassite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is brassite safe to handle?+

It contains toxic constituents. Contains arsenic, a toxic element. Handle with care, avoid inhalation of dust, and wash hands thoroughly after handling specimens. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like brassite?+

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

What minerals are found with brassite?+

Brassite commonly co-occurs with arsenolite, scorodite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does brassite form in?+

Brassite typically forms in oxidized hydrothermal arsenic-rich deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is brassite used for?+

Brassite is used in collector.

Find brassite on the map

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