Cleavelandite Identification Guide
Identify cleavelandite, the platy white variety of albite feldspar, by its bladed crystal aggregates and pegmatite setting.
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What Cleavelandite Looks Like
Cleavelandite is a distinctive platy, bladed variety of albite (sodium plagioclase feldspar). Instead of blocky crystals, it grows as thin, leaf-like or curved plates that stack and fan out into rosettes and "cockscomb" aggregates. It is typically white to colorless, sometimes pale gray or bluish, with a vitreous to pearly luster on the broad faces. The bladed, sheaf-like habit is its single most recognizable feature.
Step-by-Step Field ID Checklist
- Look for blades. Search for fans, rosettes, or stacked plates of thin white crystals — not blocky feldspar grains.
- Note the color. Usually chalky to glassy white; rarely tinted.
- Check the setting. It almost always occurs in granite pegmatites, often hosting tourmaline, lepidolite, or beryl crystals.
- Test hardness. It scratches glass faintly and is scratched by quartz (Mohs ~6–6.5).
- Find cleavage. Feldspar shows two cleavages meeting at about 90°; look for flat reflective steps.
- Look for twinning striations. Fine parallel lines (albite twinning) may show on cleavage faces.
Key Diagnostic Tests
- Hardness: 6–6.5 (feldspar range).
- Streak: White.
- Cleavage: Two good cleavages nearly at right angles (about 86–90°); this plus the platy habit is diagnostic.
- Density: ~2.62 g/cm³.
- No acid reaction, non-magnetic.
- Habit: The thin tabular/bladed crystals are the defining clue versus blocky feldspars.
Common Look-Alikes and How to Tell Them Apart
- Ordinary albite/plagioclase: Same mineral chemically, but common albite is blocky; cleavelandite is the platy, bladed habit. The form is the distinction.
- Barite or gypsum rosettes (desert rose): Barite is much denser and softer-feeling; gypsum is very soft (2) and scratched by a fingernail. Cleavelandite is hard (6–6.5).
- Muscovite mica: Mica peels into flexible elastic sheets (one perfect cleavage); cleavelandite plates are brittle feldspar with two cleavages and do not peel.
- Calcite plates: Calcite fizzes in acid and is soft (3); cleavelandite does neither.
Where It Is Found
Cleavelandite is a classic late-stage pegmatite mineral, often lining pockets where gem tourmaline, kunzite, morganite, and lepidolite grow. Notable localities include Pala and the Mesa Grande district in California, Minas Gerais in Brazil, Afghanistan/Pakistan, and the New England pegmatites where it was first described. Look in zoned granite pegmatites and their gem pockets.
Frequently asked questions
What mineral is cleavelandite?
Cleavelandite is a platy, bladed variety of albite, the sodium-rich end of the plagioclase feldspar series. It is the same mineral as albite but with a distinctive leaf-like crystal habit.
How do you identify cleavelandite?
Look for fans and rosettes of thin white brittle blades with feldspar hardness (6–6.5), two cleavages near 90 degrees, and a granite-pegmatite setting often hosting tourmaline or lepidolite.
Cleavelandite vs mica — how to tell them apart?
Mica peels into thin flexible elastic sheets with one perfect cleavage. Cleavelandite is brittle feldspar with two cleavages near right angles; its plates snap rather than peel.
Where is cleavelandite found?
It forms in late-stage granite pegmatite pockets, famously in Pala and Mesa Grande (California), Brazil, Afghanistan, and the New England pegmatites.