Hydroxylapatite is a common phosphate mineral that forms the primary mineral component of human and vertebrate bones and teeth. In geological settings, it typically appears as prismatic, hexagonal crystals in metamorphic limestones or pegmatites, often difficult to distinguish from other apatite species without chemical analysis.
Is this hydroxylapatite?
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 hydroxylapatite with a known reference. Hydroxylapatite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to subresinous, earthy.
- 4Match the color rangeCompare against the expected color range: white, wax-yellow, sea-green, brown, black.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: prismatic crystals, massive, granular, tabular.
Often confused with
Hydroxylapatite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside hydroxylapatite
Minerals reported to co-occur with hydroxylapatite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₅(PO₄)₃(OH)
- Mohs hardness
- 5
- Density
- 3.14-3.21 g/cm³
- Streak
- White
- Luster
- Vitreous to subresinous, earthy
- Transparency
- Transparent to translucent
- Crystal system
- Hexagonal
- Crystal habit
- Prismatic crystals, massive, granular, tabular
- Cleavage
- Poor on {0001} and {1010}
- Fluorescence
- Often yellow, green, or brown under SW/LW UV
- Rarity
- Common
- Uses
- Collector, Geological study, Biological research
- Host rock
- Much less common than fluorapatite
Where rockhounds find hydroxylapatite
Classic worldwide localities
- Verde Antique quarry, Holly Springs, Cherokee Co., Georgia, USA
- Midnight Owl pegmatite, White Picacho district, Maricopa Co., Arizona, USA
- Low Water Bridge Cave, Greene Co., Missouri, USA
- Chämleten (Kemmleten), near Hospental, Uri, Switzerland
- Kaiserstuhl, Baden-Württemberg, Germany
- Punta della Rossa, Val Devero, Ossola, Italy
Field-hunting tip
Where it forms: Much less common than fluorapatite. If you start seeing brushite, calcite, talc in float, you are in the right ground. Typical habit: prismatic crystals, massive, granular, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hydroxylapatite?+
Where is hydroxylapatite found?+
What rocks look like hydroxylapatite?+
What minerals are found with hydroxylapatite?+
What kind of rock does hydroxylapatite form in?+
What is hydroxylapatite used for?+
Find hydroxylapatite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
