Mosesite is a rare mercury mineral typically found as tiny, brilliant lemon-yellow octahedral crystals. It is best known for its occurrence in the mercury-rich deposits of Terlingua, Texas, where it forms in close association with other rare mercury chlorides. Collectors prize it for its vibrant color and rarity, though it is usually found only in microscopic sizes.
Is this mosesite?
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 mosesite with a known reference. Mosesite 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. Mosesite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Mosesite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: yellow, light yellow, lemon-yellow.
- 5Look at form & habitCrystal system: cubic. Typical habit: octahedral crystals, often as crusts or tiny groupings.
Often confused with
Mosesite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside mosesite
Minerals reported to co-occur with mosesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Hg₂NH₂Cl₂SO₄
- Mohs hardness
- 3
- Density
- 6.8-6.9 g/cm³
- Streak
- White
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Octahedral Crystals, Often as Crusts or Tiny Groupings
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Mercury-bearing Hydrothermal Veins in Limestone
- Typical price
- $100-500 per specimen
Where rockhounds find mosesite
Classic worldwide localities
- Terlingua, Texas, USA
Field-hunting tip
Look in mercury-bearing hydrothermal veins in limestone country — that is the host setting where mosesite typically forms. If you start seeing calomel, terlinguaite, eglestonite in float, you are in the right ground. Field specimens usually show a octahedral crystals, often as crusts or tiny groupings habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify mosesite?+
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Find mosesite on the map
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