Criddleite is an extremely rare sulfosalt mineral found in gold-bearing hydrothermal deposits. It is typically identified through microscopic examination of polished sections, appearing as small, grey metallic grains intergrown with other minerals like aurostibite and stibnite.
Is this criddleite?
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 criddleite with a known reference. Criddleite sits at Mohs 3-3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: anhedral grains, lath, microscopic crystals.
Often confused with
Criddleite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Criddleite leaves black, Aurostibite leaves bronze.
How to tell apart: Criddleite is noticeably harder (Mohs 3-3.5 vs. 2); streak differs, so Criddleite leaves black, Stibnite leaves lead-gray.
How to tell apart: Gudmundite is the harder of the two (Mohs ~5-6 vs. 3-3.5); streak differs, so Criddleite leaves black, Gudmundite leaves grayish black.
Often found alongside criddleite
Minerals reported to co-occur with criddleite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₂Au₃TlSb₁₀S₁₀
- Mohs hardness
- 3-3.5
- Density
- 6.86 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Anhedral grains, lath, microscopic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A primary hydrothermal mineral in a complex gold deposits
Where rockhounds find criddleite
Classic worldwide localities
- Hemlo gold deposit, Thunder Bay district, Ontario, Canada
- Viges Au–Sb deposit, Creuse, France
Field-hunting tip
Where it forms: A primary hydrothermal mineral in a complex gold deposits. If you start seeing aurostibite, gold, antimony in float, you are in the right ground. Typical habit: anhedral grains, lath, microscopic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find criddleite on the map
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