Cacoxenite is highly prized by collectors for its stunning, radiating sprays of golden-yellow needles that often look like tiny sunbursts. It is most frequently found as an inclusion within quartz crystals, known as super seven or amethyst cacoxenite, where the delicate plumes are preserved within the clear host. It typically forms in the oxidized zones of iron-rich mineral deposits.
Is this cacoxenite?
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 cacoxenite with a known reference. Cacoxenite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cacoxenite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Cacoxenite typically shows a silky luster.
- 4Match the color rangeCompare against the expected color range: yellow, golden-yellow, orange, brown.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: radiating fibrous tufts, spherical clusters, botryoidal.
Often confused with
Cacoxenite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Iron Ore is the harder of the two (Mohs 5-6.5 vs. 3-4); streak differs — Cacoxenite leaves yellow, Iron Ore leaves reddish-brown to black; luster reads silky on Cacoxenite and metallic to submetallic on Iron Ore.
How to tell apart: Streak differs — Cacoxenite leaves yellow, Wavellite leaves white; luster reads silky on Cacoxenite and vitreous on Wavellite.
Often found alongside cacoxenite
Minerals reported to co-occur with cacoxenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺₂₄AlO₆(PO₄)₁₇(OH)₁₂·17H₂O
- Mohs hardness
- 3-4
- Density
- 2.26-2.5 g/cm³
- Streak
- Yellow
- Luster
- Silky
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Radiating Fibrous Tufts, Spherical Clusters, Botryoidal
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Study Mineral
- Host rock
- Iron-rich Sedimentary Deposits, Oxidized Phosphate Zones
- Typical price
- $10-50 per small specimen, $100+ for high-quality clusters
Where rockhounds find cacoxenite
Classic worldwide localities
- Czech Republic
- Germany
- Belgium
- USA
- Brazil
Field-hunting tip
Look in iron-rich sedimentary deposits, oxidized phosphate zones country — that is the host setting where cacoxenite typically forms. If you start seeing quartz, magnetite, strengite in float, you are in the right ground. Field specimens usually show a radiating fibrous tufts, spherical clusters, botryoidal habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cacoxenite?+
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What rocks look like cacoxenite?+
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Find cacoxenite on the map
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