Chursinite is a rare mercury arsenate that forms yellow-brown to orange-brown grains. It occurs in the oxidized zone of a Sb-As-Hg deposit. It was first described from Khaydarkan deposit, Fergana Valley, Alai Range, Kyrgyzstan.
Is this chursinite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch chursinite with a known reference. Chursinite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: grayish yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine, nearly.
- 4Match the color rangeCompare against the expected color range: yellow brown, orange brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tarnishes.
Often confused with
Chursinite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Chursinite is noticeably harder (Mohs ~3 vs. 1.5-2); streak differs, so Chursinite leaves grayish yellow, Gypsum leaves white; luster reads adamantine, nearly on Chursinite and subvitreous, pearly on {010} cleavages, silky if fibrous on Gypsum.
How to tell apart: Streak differs, so Chursinite leaves grayish yellow, Pharmacolite leaves white; luster reads adamantine, nearly on Chursinite and vitreous, pearly on cleavages on Pharmacolite.
Often found alongside chursinite
Minerals reported to co-occur with chursinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Hg¹⁺Hg²⁺(AsO₄)
- Mohs hardness
- ~3
- Density
- 9.06 g/cm³
- Colors
- Streak
- Grayish yellow
- Luster
- Adamantine, nearly
- Transparency
- Transparent in thin fragments
- Crystal system
- Monoclinic
- Crystal habit
- Tarnishes
- Cleavage
- One, parallel to elongation
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the oxidized zone of a Sb–As–Hg deposit
Where rockhounds find chursinite
Classic worldwide localities
- Khaydarkan deposit, Fergana Valley, Alai Range, Kyrgyzstan
Field-hunting tip
Where it forms: In the oxidized zone of a Sb–As–Hg deposit. If you start seeing calomel, eglestonite, terlinguaite in float, you are in the right ground. Typical habit: tarnishes. Train your eye for that shape before scanning the outcrop.
Common questions
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Find chursinite on the map
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