Harrisonite is an extremely rare calcium iron silicate phosphate found primarily in alkaline volcanic environments. Collectors typically look for its distinct, thin platy, metallic crystals that appear in association with other rare-earth bearing minerals. Due to its scarcity, it is almost exclusively found in professional mineral collections.
Is this harrisonite?
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 harrisonite with a known reference. Harrisonite sits at Mohs <5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow brown, orange brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: anhedral grains, selvage.
Often confused with
Harrisonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Harrisonite leaves pale yellow, Ilmenite leaves black to reddish brown; luster reads vitreous on Harrisonite and metallic to submetallic on Ilmenite.
How to tell apart: Streak differs, so Harrisonite leaves pale yellow, Hematite leaves cherry-red or reddish brown; luster reads vitreous on Harrisonite and metallic or submetallic to dull on Hematite.
Often found alongside harrisonite
Minerals reported to co-occur with harrisonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaFe₆Si₂P₂O₁₆
- Mohs hardness
- <5
- Density
- 4.02 g/cm³
- Colors
- Streak
- Pale yellow
- Luster
- Vitreous
- Transparency
- Translucent to transparent on thin edges
- Crystal system
- Trigonal
- Crystal habit
- Anhedral grains, selvage
- Cleavage
- Observed, very poor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A minor but wide-spread constituent in a layered iron silicate-quartz-apatite body in gneisses, probably a shaly and phosphatic iron formation metamorphosed to the granulite facies
Where rockhounds find harrisonite
Classic worldwide localities
- Arcedeckne Island, near the Boothia Peninsula, District of Franklin, Arctic Canada
Field-hunting tip
Where it forms: A minor but wide-spread constituent in a layered iron silicate-quartz-apatite body in gneisses, probably a shaly and phosphatic iron formation metamorphosed to the granulite facies. If you start seeing fluorapatite, quartz, fayalite in float, you are in the right ground. Typical habit: anhedral grains, selvage. Train your eye for that shape before scanning the outcrop.
Common questions
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Find harrisonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
