Fluorapophyllite-(Cs) is a rare member of the apophyllite group characterized by significant cesium substitution in the crystal structure. It is most commonly found in highly specific alkaline environments, particularly the Darai-Pioz locality in Tajikistan, where it forms distinct, transparent tetragonal crystals. Collectors identify this species primarily through chemical analysis due to its visual similarity to more common apophyllite species.
Is this fluorapophyllite-(cs)?
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 fluorapophyllite-(cs) with a known reference. Fluorapophyllite-(Cs) sits at Mohs 4.5-5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Fluorapophyllite-(Cs) leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Fluorapophyllite-(Cs) typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, pinkish.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular to prismatic crystals, often with prominent pyramidal faces.
Often confused with
Fluorapophyllite-(Cs) vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside fluorapophyllite-(cs)
Minerals reported to co-occur with fluorapophyllite-(cs). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KCsCa₄Si₈O₂₀F·8H₂O
- Mohs hardness
- 4.5-5
- Density
- 2.5-2.6 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular to Prismatic Crystals, Often with Prominent Pyramidal Faces
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Pegmatites and Miarolitic Cavities
- Typical price
- $50-500 depending on specimen size and clarity
Where rockhounds find fluorapophyllite-(cs)
Classic worldwide localities
- Darai-Pioz Glacier, Tajikistan
Field-hunting tip
Look in alkaline pegmatites and miarolitic cavities country — that is the host setting where fluorapophyllite-(cs) typically forms. If you start seeing quartz, calcite, pectolite in float, you are in the right ground. Field specimens usually show a tabular to prismatic crystals, often with prominent pyramidal faces habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fluorapophyllite-(cs)?+
Where is fluorapophyllite-(cs) found?+
How much is fluorapophyllite-(cs) worth?+
What rocks look like fluorapophyllite-(cs)?+
What minerals are found with fluorapophyllite-(cs)?+
What kind of rock does fluorapophyllite-(cs) form in?+
What is fluorapophyllite-(cs) used for?+
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