Goyazite is a strontium aluminum phosphate member of the alunite supergroup, often found as small, sharp, rhombohedral crystals. It is most frequently encountered by collectors in diamond-bearing gravels or as an accessory mineral in hydrothermal veins. Because its appearance can be very similar to other phosphate group minerals, positive identification often requires chemical testing.
Is this goyazite?
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 goyazite with a known reference. Goyazite sits at Mohs 4.5-5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: greasy to resinous, pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: colorless, lemon yellow, pink.
- 5Look at form & habitCrystal system: trigonal. Typical habit: blocky, disseminated.
Often confused with
Goyazite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads greasy to resinous, pearly on cleavages on Goyazite and vitreous, dull to chalky when massive on Crandallite.
How to tell apart: Goyazite is noticeably harder (Mohs 4.5-5 vs. 3.5); streak differs, so Goyazite leaves white, Dussertite leaves yellow; luster reads greasy to resinous, pearly on cleavages on Goyazite and vitreous to resinous on Dussertite.
Often found alongside goyazite
Minerals reported to co-occur with goyazite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SrAl₃(PO₄)₂(OH)₅·H₂O
- Mohs hardness
- 4.5-5
- Density
- 3.26 g/cm³
- Streak
- White
- Luster
- Greasy to resinous, pearly on cleavages
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Blocky, disseminated
- Cleavage
- Perfect on {0001}
- Rarity
- Uncommon
- Uses
- Collector, Mineralogical research
- Host rock
- In granite pegmatites; from hydrothermal argillic alteration zones; in kaolinitic claystones derived from air-fall volcanic tuffs; in carbonatites; detrital
Where rockhounds find goyazite
Classic worldwide localities
- Palermo #1 mine, near North Groton, Grafton Co., New Hampshire, USA
- Oxford Co., in the Bennett quarry, Buckfield, the Harvard quarry, Greenwood, the Mt. Mica quarry, Paris, at Lord Hill, Stoneham, Maine, USA
- Apex mine, near St. George, Washington Co., Utah, USA
- Serra de Congonhas, near Diamantina, Minas Gerais, and at Alto Bernardino, about 20 km northwest of Picuí, Paraíba, Brazil
- Dakota hogback, from Turkey Creek, Jefferson Co., to Boxelder Creek, Larimer Co., Colorado
- Rapid Creek-Big Fish River area, Yukon Territory, Canada
Field-hunting tip
Where it forms: In granite pegmatites; from hydrothermal argillic alteration zones; in kaolinitic claystones derived from air-fall volcanic tuffs; in carbonatites; detrital. If you start seeing herderite, apatite, quartz in float, you are in the right ground. Typical habit: blocky, disseminated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify goyazite?+
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Find goyazite on the map
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