Albitite Identification Guide

What Albitite Looks Like

Albitite is a light-colored rock composed almost entirely of the sodium feldspar albite, usually formed by sodium metasomatism (albitization) of pre-existing rocks, or as a late igneous/pegmatitic differentiate.

• Color: white, cream, pale gray, sometimes pinkish or greenish.
• Luster: the rock surface sparkles slightly from feldspar cleavage faces catching light.
• Texture: typically fine- to medium-grained and sugary (saccharoidal); can be coarse where pegmatitic. Quartz and dark minerals are scarce.
• Form: dikes, veins, and replacement zones; an overall monomineralic, pale, even-textured rock.

Step-by-Step Field ID Checklist

1. Note the overall paleness. Albitite is leucocratic — almost all light feldspar with very few dark minerals.
2. Confirm feldspar, not quartz. Look (hand lens) for cleavage faces that flash light; albite cleaves, quartz does not.
3. Check for twin striations. Tiny parallel lines on feldspar grains indicate plagioclase (albite).
4. Test hardness. Grains around Mohs 6–6.5 scratch glass but are scratched by a quartz pebble.
5. Acid test. No fizz (rules out marble/carbonate).
6. Setting. Look for it as a vein/dike or an altered zone, often near granites, shear zones, or pegmatites.

Key Diagnostic Tests

• Hardness: dominated by albite, ~6–6.5.
• Cleavage in grains: two good cleavages near 90 degrees — confirms feldspar rock, not quartzite.
• Composition: >90% albite; little quartz, little dark mineral.
• Density: ~2.6, light.
• Acid: none.
• Magnetism: none significant.

Common Look-Alikes and How to Tell Them Apart

• Aplite: a fine-grained granitic rock, but aplite contains abundant quartz and K-feldspar; albitite is dominated by albite with little quartz. Check for shimmering cleavage (feldspar) versus glassy grains with no cleavage (quartz).
• Quartzite: made of interlocking quartz with no cleavage and hardness 7 throughout; albitite shows feldspar cleavage flashes and is slightly softer.
• Marble: soft (3) and fizzes in acid; albitite does neither.
• Trondhjemite/leucogranite: also pale, but these carry significant quartz and are true plutonic rocks; albitite is near-monomineralic albite, often metasomatic.
• Adinole: a related sodic metasomatic rock, but adinole is aphanitic and flinty and tied specifically to dolerite contacts; albitite is coarser and more clearly feldspar-granular.

Where Albitite Is Found

Albitite occurs where sodium-rich fluids have albitized granites, gneisses, or other rocks — commonly along shear zones, in pegmatite margins, and in association with certain uranium, rare-earth, and gold deposits. Examples are known from Scandinavia, the Mont Blanc and Alpine regions, Brazil, and many shear-hosted ore districts worldwide. Look for pale, sugary, feldspar-rich veins and replacement bodies cutting darker host rock.