Vermiculite — (Mg,Fe,Al)₃(Si,Al)₄O₁₀(OH)₂·4H₂O, a weathered mica that holds water. Heated, it puffs into worm-like strands.

Bronze-brown, pearly, Mohs 1.5–2.
Swipe for the spin.

Specimen image: AI-generated.
https://apps.apple.com/us/app/rockspin/id6747876962
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