Carlfriesite is a rare calcium tellurite mineral discovered in the oxidized zones of tellurium-rich ore deposits. It typically forms delicate, yellow prismatic crystals or radial clusters that are highly prized by systematic mineral collectors.
Is this carlfriesite?
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 carlfriesite with a known reference. Carlfriesite 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. Streak: very pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, radial aggregates.
Often confused with
Carlfriesite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Carlfriesite leaves very pale yellow, Quetzalcoatlite leaves pale blue, almost white; luster reads adamantine on Carlfriesite and pearly to dull on Quetzalcoatlite.
How to tell apart: Streak differs, so Carlfriesite leaves very pale yellow, Rodalquilarite leaves greenish yellow; luster reads adamantine on Carlfriesite and greasy on Rodalquilarite.
Often found alongside carlfriesite
Minerals reported to co-occur with carlfriesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaTe₂TeO₈
- Mohs hardness
- 3.5
- Density
- 6.3 g/cm³
- Colors
- Streak
- Very pale yellow
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals, radial aggregates
- Cleavage
- On {010}, fair
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In cavities in an oxidized hydrothermal Au–Te deposit in intensely silicified brecciated rhyolite vitrophyre
Where rockhounds find carlfriesite
Classic worldwide localities
- Oriental (Bambollita) mine, northeast of the Moctezuma (Bambolla) mine, 12 km south of Moctezuma, Sonora, Mexico
Field-hunting tip
Where it forms: In cavities in an oxidized hydrothermal Au–Te deposit in intensely silicified brecciated rhyolite vitrophyre. If you start seeing cerussite, chlorargyrite, argentian gold in float, you are in the right ground. Typical habit: prismatic crystals, radial aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find carlfriesite on the map
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