Cyrilovite is a rare phosphate mineral typically found as small, bright yellow, pseudo-octahedral crystals in phosphate-rich pegmatites. Collectors look for its characteristic tetragonal habit and association with other secondary phosphate minerals. It is primarily a specimen mineral of interest to advanced systematic collectors.
Is this cyrilovite?
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 cyrilovite with a known reference. Cyrilovite sits at Mohs 4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow, orange yellow, brown.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: massive, pseudo cubic.
Often confused with
Cyrilovite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Wardite is the harder of the two (Mohs 5 vs. 4); streak differs, so Cyrilovite leaves yellow, Wardite leaves white.
How to tell apart: Gorceixite is the harder of the two (Mohs 6 vs. 4); streak differs, so Cyrilovite leaves yellow, Gorceixite leaves white.
Often found alongside cyrilovite
Minerals reported to co-occur with cyrilovite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaFe³⁺₃(PO₄)₂(OH)₄·2H₂O
- Mohs hardness
- 4
- Density
- 3.081-3.096 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Massive, pseudo cubic
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare accessory mineral in some oxidizing phosphate-bearing granite pegmatites and iron deposits
Where rockhounds find cyrilovite
Classic worldwide localities
- Palermo #1 mine, near North Groton, Grafton Co., New Hampshire, and in the Tip Top mine, 8.5 km southwest of Custer, Custer Co., South Dakota, USA
- Cyrilov pegmatite, Velké Meźiřiči, Czech Republic
- Gunheath china clay pit, St. Austell, Cornwall, England
- Rochefort-en-Terre, Bretagne, France
- Vermilhas pegmatite, Vouzela, Portugal
- Mangualde pegmatite, near Mesquitela, Portugal
Field-hunting tip
Where it forms: A rare accessory mineral in some oxidizing phosphate-bearing granite pegmatites and iron deposits. If you start seeing dufrénite, frondelite, phosphosiderite in float, you are in the right ground. Typical habit: massive, pseudo cubic. Train your eye for that shape before scanning the outcrop.
Common questions
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Find cyrilovite on the map
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