Cacoxenite
Real mineral · rare · (Fe+++,Al)₂₅(PO₄)₁₇O₆(OH)₁₂•75(H₂O)
An iron phosphate in golden needle-like tufts, best known not for itself but as the inclusion that turns quartz and amethyst into the stone traders call super seven. Its name means guest, for the iron it contaminates.
Identity
- Formula
- (Fe+++,Al)₂₅(PO₄)₁₇O₆(OH)₁₂•75(H₂O)
- Chemical class
- phosphate
Crystallography
- Crystal system
- hexagonal
- Habits
- acicular, fibrous, botryoidal
- Fracture
- uneven
Physical properties
- Mohs hardness
- 3
- Density
- 2.84 g/cm³
- Luster
- silky
- Colors
- brownish yellow, green, yellow, golden yellow, red yellow
- Streak
- yellow
- Transparency
- translucent
Geology
- Origins
- sedimentary, hydrothermal
- Host rocks
- iron ore, pegmatite
- Associated minerals
- Goethite, Quartz, Amethyst, Apatite
- Geography
- Czech Republic, USA, Brazil
Classification
- Rarity
- rare
- Gem quality
- No
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