Mcalpineite is a rare copper tellurate mineral typically found as tiny green to yellow-green grains within oxidized gold-telluride ore deposits. It is primarily a collector's mineral and is rarely seen in crystals, usually appearing as encrustations or granular masses in association with other tellurium minerals.
Is this mcalpineite?
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 mcalpineite with a known reference. Mcalpineite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Mcalpineite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Mcalpineite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: green, yellow-green.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive, anhedral grains.
Often confused with
Mcalpineite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Mcalpineite is noticeably harder (Mohs 3.5 vs. 2); streak differs — Mcalpineite leaves light green, Tellurite leaves white; luster reads vitreous on Mcalpineite and adamantine on Tellurite.
How to tell apart: Emmonsite is the harder of the two (Mohs 5 vs. 3.5); streak differs — Mcalpineite leaves light green, Emmonsite leaves pale yellow.
Often found alongside mcalpineite
Minerals reported to co-occur with mcalpineite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃TeO₆
- Mohs hardness
- 3.5
- Density
- 7.5 g/cm³
- Colors
- Streak
- Light Green
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Cubic
- Crystal habit
- Massive, Anhedral Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Tellurium-bearing Hydrothermal Gold Veins
- Typical price
- $50-300 per specimen
Where rockhounds find mcalpineite
Classic worldwide localities
- McAlpine mine, California, USA
- Tombstone district, Arizona, USA
- Moctezuma, Sonora, Mexico
Field-hunting tip
Look in oxidized tellurium-bearing hydrothermal gold veins country — that is the host setting where mcalpineite typically forms. If you start seeing tellurium, emmonsite, dugganite in float, you are in the right ground. Field specimens usually show a massive, anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find mcalpineite on the map
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