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, so 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, so 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, 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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