Ottensite is an extremely rare antimony sulfosalt that typically occurs as delicate, hair-like acicular crystals. It is highly sought after by advanced collectors for its striking orange-red color and association with other rare antimony minerals.

Hardness

Mohs

Luster

Adamantine

Streak

Orange

Transparency

Transparent

mineralrare

Ottensite

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

Is this ottensite?

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 ottensite with a known reference. Ottensite 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. Ottensite leaves a orange streak.
3
Read the luster
Hold the specimen under a strong light. Ottensite typically shows a adamantine luster.
4
Match the color range
Compare against the expected color range: red, orange-red.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: acicular or hair-like crystals.

Often confused with

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

mineral

Stibnite

Mohs 2

How to tell apart: Streak differs — Ottensite leaves orange, Stibnite leaves lead-gray; luster reads adamantine on Ottensite and metallic on Stibnite.

How to tell apart: Streak differs — Ottensite leaves orange, Kermesite leaves brownish-red.

Compare →

Often found alongside ottensite

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

All properties

Chemical formula: Na₃Sb₃S₆·3H₂O
Mohs hardness: 2
Density: 4.57 g/cm³
Colors: Red Orange-red
Streak: Orange
Luster: Adamantine
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Acicular or Hair-like Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Antimony-rich Hydrothermal Deposits
Typical price: $100-500 for small thumbnail specimens

Where rockhounds find ottensite

Classic worldwide localities

Hunan Province, China

Field-hunting tip

Look in antimony-rich hydrothermal deposits country — that is the host setting where ottensite typically forms. If you start seeing stibnite, kermesite, valentinite in float, you are in the right ground. Field specimens usually show a acicular or hair-like crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify ottensite?+

Mohs hardness is 2. It typically shows a adamantine luster. The streak is orange. Common colors include red, orange-red.

Where is ottensite found?+

Notable localities include Hunan Province, China.

How much is ottensite worth?+

Typical asking prices fall in the range of $100-500 for small thumbnail specimens. Quality, size, and provenance can move individual specimens well outside that range.

Is ottensite safe to handle?+

It contains toxic constituents. Contains antimony and sulfur; avoid inhalation of dust, wash hands thoroughly after handling, and store in a sealed container. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like ottensite?+

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

What minerals are found with ottensite?+

Ottensite commonly co-occurs with Stibnite, Kermesite, Valentinite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ottensite form in?+

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

What is ottensite used for?+

Ottensite is used in collector.

Find ottensite on the map

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