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. Carlfriesite leaves a very pale yellow streak.
- 3Read the lusterHold the specimen under a strong light. Carlfriesite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: yellow, pale 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 pale 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
- CaTe₂O₅
- 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
- Fair On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Tellurium-bearing Hydrothermal Deposits
Where rockhounds find carlfriesite
Classic worldwide localities
- Moctezuma Mine, Sonora, Mexico
Field-hunting tip
Look in oxidized tellurium-bearing hydrothermal deposits country, the host setting where carlfriesite typically forms. If you start seeing tellurite, paratellurite, quetzalcoatlite in float, you are in the right ground. Field specimens usually show a prismatic crystals, radial aggregates habit, so 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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