Rock and Mineral Identification Reference

How to Identify Muscovite (White Mica): Hardness, Streak, Luster and Tests

Quick answer

Muscovite (White Mica) (mineral): 6 identifying properties, and how to tell it from Biotite, quoted from geology department and survey sources.

Updated 2026-09-10 · Sources: University of Minnesota Common Minerals

Scratch, streak and acid tests mark the specimen, and some produce sharp fragments or dust. Wear eye protection, work in a ventilated space, keep acid off skin, and never taste a mineral you have not already identified.

How to Identify Muscovite (White Mica): Hardness, Streak, Luster and Tests — Photo: Robert M. Lavinsky · CC BY-SA 3.0 · source

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What are the key facts?

Type: Mineral
Mohs hardness: 2–2.5 (very soft)
Streak: White
Luster: Vitreous to pearly luster.
Color: Usually colorless, white, or silver; occasionally yellow or brown.
Cleavage or fracture: One direction of perfect cleavage, splitting into thin sheets.
Specific gravity: 2.8–3

What Muscovite (White Mica) looks like

The properties that identify Muscovite (White Mica) — mohs hardness: 2–2.5 (very soft); streak: White; luster: Vitreous to pearly luster; color: Usually colorless, white, or silver; occasionally yellow or brown; cleavage or fracture: One direction of perfect cleavage, splitting into thin sheets; specific gravity: 2.8–3. Hardness, streak and cleavage are the reliable ones; color alone rarely settles it.

Often confused with

[Biotite (Black Mica)](/lookup/rocks-and-minerals/biotite): Muscovite is colorless, silvery-white, or light-colored; biotite is typically brown to black.

Where it is found in North America

Common in granites, granite pegmatites, and metamorphic rocks such as phyllites and schists; also found in sedimentary rocks like sandstone and shale.

How to photograph it for identification

Photograph a fresh, unweathered surface in daylight, then a second shot of any crystal faces or broken edge. Include a coin for scale. If you did a streak test, photograph the streak next to the specimen. The app suggests the likely mineral or rock; confirm with hardness and the tests above before you label it.

FAQ

How hard is Muscovite (White Mica) on the Mohs scale?

2–2.5 (very soft). A fingernail is about 2.5, a copper coin about 3, a steel knife 5.5 and glass about 5.5, so test against those.

What color streak does Muscovite (White Mica) leave?

White. Rub the specimen on an unglazed porcelain tile; the powder color is the streak, and it is more consistent than the specimen color.

How do I tell Muscovite (White Mica) from Biotite?

Muscovite is colorless, silvery-white, or light-colored; biotite is typically brown to black.

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Sources

University of Minnesota Common Mineralscommonminerals.esci.umn.edu/minerals-g-m/muscovite
University of Minnesota Common Mineralscommonminerals.esci.umn.edu/minerals-f/biotite

Compiled by the RockLens editorial team

Every fact on this page is taken from the sources listed above; numbers and prices are copied from the source, and prices name the guide or auction and its date. Research and drafting were assisted by AI, and each claim was then checked against the cited sources. Checked 2026-09-10. We do not buy, sell or grade items; the app identifies what you photograph and points you to these references.