Pinchite is a rare mercury oxychloride mineral known primarily from the Terlingua mining district in Texas. It typically occurs as small, transparent, black to dark brown tabular crystals associated with other rare mercury minerals in limestone cavities.
Is this pinchite?
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 pinchite with a known reference. Pinchite sits at Mohs 1-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: reddish brown.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: black, black brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, subhedral grains.
Often confused with
Pinchite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Pinchite leaves reddish brown, Eglestonite leaves yellow or greenish yellow, rapidly becoming black; luster reads adamantine on Pinchite and brilliant adamantine to resinous on Eglestonite.
How to tell apart: Kleinite is the harder of the two (Mohs 3.5-4 vs. 1-2); streak differs, so Pinchite leaves reddish brown, Kleinite leaves sulfur-yellow.
Often found alongside pinchite
Minerals reported to co-occur with pinchite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Hg₅Cl₂O₄
- Mohs hardness
- 1-2
- Density
- 9.5 g/cm³
- Colors
- Streak
- Reddish brown
- Luster
- Adamantine
- Transparency
- Opaque, transparent in thin fragments
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular crystals, subhedral grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in a hydrothermal mercury deposit
Where rockhounds find pinchite
Classic worldwide localities
- Terlingua, Brewster Co., Texas, USA
Field-hunting tip
Where it forms: A secondary mineral in a hydrothermal mercury deposit. If you start seeing montroydite, terlinguaite in float, you are in the right ground. Typical habit: tabular crystals, subhedral grains. Train your eye for that shape before scanning the outcrop.
Common questions
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Find pinchite on the map
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