Jalpaite is a rare silver-copper sulfide that typically appears as lead-gray to black anhedral masses within hydrothermal veins. It is most commonly found in association with acanthite and stromeyerite, often requiring X-ray diffraction or chemical analysis for positive identification due to its unremarkable appearance.
Is this jalpaite?
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 jalpaite with a known reference. Jalpaite sits at Mohs 2-2.5, 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: gray, dark gray.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: massive, anhedral grains.
Often confused with
Jalpaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Jalpaite leaves black, Stromeyerite leaves steel-gray.
How to tell apart: Chalcopyrite is the harder of the two (Mohs 3.5-4 vs. 2-2.5); streak differs, so Jalpaite leaves black, Chalcopyrite leaves greenish black.
Often found alongside jalpaite
Minerals reported to co-occur with jalpaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₃CuS₂
- Mohs hardness
- 2-2.5
- Density
- 6.82-6.85 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Massive, anhedral grains
- Cleavage
- Prismatic, good
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Formed under low-temperature (below 117°C) hydrothermal conditions
Where rockhounds find jalpaite
Classic worldwide localities
- Payrock mine, Silver Plume, Clear Creek Co., Colorado, USA
- Bulldog Mountain mine, Creede, Mineral Co., Colorado, USA
- Hock Hocking mine, near Alma, Park Co., Colorado, USA
- Boulder Co., at the E.C. Hite mine, and the Caribou mine, near Nederland, Colorado, USA
- La Leonora mine, Jalpa, Zacatecas (type locality), and at La Mesa, Chihuahua, Mexico
- Kongsberg, Norway
Field-hunting tip
Where it forms: Formed under low-temperature (below 117°C) hydrothermal conditions. If you start seeing acanthite, mckinstryite, galena in float, you are in the right ground. Typical habit: massive, anhedral grains. Train your eye for that shape before scanning the outcrop.
Common questions
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Find jalpaite on the map
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