Mcnearite is a rare secondary arsenate mineral typically found as delicate acicular crystals or radial tufts in hydrothermal veins. It is predominantly associated with other arsenic-bearing minerals and is highly prized by collectors for its rarity and crystal structure. Collectors should handle it with care due to its arsenic content.
Is this mcnearite?
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 mcnearite with a known reference. Mcnearite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Mcnearite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Mcnearite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: triclinic. Typical habit: acicular crystals, radial aggregates.
Often confused with
Mcnearite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Mcnearite and adamantine on Pharmacosiderite.
How to tell apart: Streak differs — Mcnearite leaves white, Yukonite leaves yellowish-brown; luster reads vitreous on Mcnearite and resinous on Yukonite.
Often found alongside mcnearite
Minerals reported to co-occur with mcnearite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₅(AsO₄)₂(HAsO₄)₂·4H₂O
- Mohs hardness
- 2
- Density
- 2.16 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Acicular Crystals, Radial Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Arsenic-bearing Deposits
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find mcnearite
Classic worldwide localities
- Ste. Marie-aux-Mines, France
- Jáchymov, Czech Republic
- Wittichen, Germany
Field-hunting tip
Look in hydrothermal arsenic-bearing deposits country — that is the host setting where mcnearite typically forms. If you start seeing arsenolite, pharmacolite, haidingerite in float, you are in the right ground. Field specimens usually show a acicular crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find mcnearite on the map
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