Blossite is a rare copper selenite mineral found primarily as a sublimation product in volcanic fumaroles. It typically appears as small black crystals or crusts, often associated with other rare selenium-bearing species. It is a highly specialized collector's mineral that requires careful handling due to its chemical composition.

Hardness

Mohs

Luster

Submetallic

Streak

Black

Transparency

Opaque

mineralrare

Blossite

Hardness: 3
Luster: Submetallic
Streak: Black
Transparency: Opaque

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Is this blossite?

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 blossite with a known reference. Blossite 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. Blossite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Blossite typically shows a submetallic luster.
4
Match the color range
Compare against the expected color range: black.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, massive, granular.

Often confused with

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

mineral

Chalcomenite

Mohs 2.5

How to tell apart: Streak differs — Blossite leaves black, Chalcomenite leaves pale blue; luster reads submetallic on Blossite and vitreous on Chalcomenite.

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Often found alongside blossite

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

All properties

Chemical formula: α-Cu₂SeO₃
Mohs hardness: 3
Density: 5.5 g/cm³
Colors: Black
Streak: Black
Luster: Submetallic
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Massive, Granular
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Volcanic Fumaroles
Typical price: $50-500 depending on specimen quality

Where rockhounds find blossite

Classic worldwide localities

Izalco Volcano, El Salvador

Field-hunting tip

Look in volcanic fumaroles country — that is the host setting where blossite typically forms. If you start seeing chalcomenite, selenite, cuprite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify blossite?+

Mohs hardness is 3. It typically shows a submetallic luster. The streak is black. Common colors include black.

Where is blossite found?+

Notable localities include Izalco Volcano, El Salvador.

How much is blossite worth?+

Typical asking prices fall in the range of $50-500 depending on specimen quality. Quality, size, and provenance can move individual specimens well outside that range.

Is blossite safe to handle?+

It contains toxic constituents. Contains copper and selenium. Wash hands thoroughly after handling and avoid ingestion or inhalation of dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like blossite?+

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

What minerals are found with blossite?+

Blossite commonly co-occurs with Chalcomenite, Selenite, Cuprite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does blossite form in?+

Blossite typically forms in volcanic fumaroles. Working float back to the host body is the standard way to chase a fresh occurrence.

What is blossite used for?+

Blossite is used in collector.

Find blossite on the map

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