Fluorellestadite is a rare member of the apatite group characterized by significant silicon and sulfur substitution. It is primarily known for its distinct fluorescent properties, often glowing brilliantly under ultraviolet light. Collectors typically find it in contact-metamorphosed limestone or skarn deposits associated with calc-silicate minerals.
Is this fluorellestadite?
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 fluorellestadite with a known reference. Fluorellestadite sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white with weak bluish tint.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to greasy.
- 4Match the color rangeCompare against the expected color range: blue, pale bluish green.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: prismatic crystals, massive, granular.
Often confused with
Fluorellestadite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside fluorellestadite
Minerals reported to co-occur with fluorellestadite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₅(SiO₄)₁.₅(SO₄)₁.₅F
- Mohs hardness
- 4.5
- Density
- 3.03 g/cm³
- Colors
- BluePale bluish green
- Streak
- White with weak bluish tint
- Luster
- Vitreous to greasy
- Transparency
- Transparent to translucent
- Crystal system
- Hexagonal
- Crystal habit
- Prismatic crystals, massive, granular
- Cleavage
- Poor
- Fluorescence
- Strong violet or orange-yellow under UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed in burned fragments of petrified wood in coal dumps (Kopeysk, Russia)
Where rockhounds find fluorellestadite
Classic worldwide localities
- Crestmore, Riverside Co., California, and Franklin, Sussex Co., New Jersey, USA
- Mines around Kopeysk, Chelyabinsk coal basin, Southern Ural Mountains, Russia
- Bellerberg volcano, two km north of Mayen, Eifel district, Germany
Field-hunting tip
Where it forms: Formed in burned fragments of petrified wood in coal dumps (Kopeysk, Russia). If you start seeing lime, periclase, magnesioferrite in float, you are in the right ground. Typical habit: prismatic crystals, massive, granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fluorellestadite?+
Where is fluorellestadite found?+
What rocks look like fluorellestadite?+
What minerals are found with fluorellestadite?+
What kind of rock does fluorellestadite form in?+
What is fluorellestadite used for?+
Find fluorellestadite on the map
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