Francolite is a carbonate-rich variety of fluorapatite that often forms the primary mineral constituent of sedimentary phosphorite beds. Collectors typically find it in earthy, botryoidal, or massive habits, frequently associated with fossil remains or phosphate-rich sediments.
Is this francolite?
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 francolite with a known reference. Francolite 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.
- 4Match the color rangeCompare against the expected color range: white, gray, yellow, brown, green.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: massive, encrusting, botryoidal, or as a replacement in fossilized material.
Often confused with
Francolite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside francolite
Minerals reported to co-occur with francolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₅(PO₄,CO₃)₃F
- Mohs hardness
- 5
- Density
- 3.1-3.2 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Massive, encrusting, botryoidal, or as a replacement in fossilized material
- Cleavage
- Indistinct
- Fluorescence
- Often yellow or green under UV
- Rarity
- Common
- Uses
- Collector, Scientific research, Geological indicator
- Host rock
- sedimentary phosphorite deposits
Where rockhounds find francolite
3 mapped spotsClassic worldwide localities
- Florida, USA
- Morocco
- Russia
- England
- Peru
Field-hunting tip
Where it forms: sedimentary phosphorite deposits. If you start seeing calcite, dolomite, quartz in float, you are in the right ground. Typical habit: massive, encrusting, botryoidal, or as a replacement in fossilized material. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
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Find francolite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
