mineral

Likely banded tourmaline

Tourmaline-group mineral, probably elbaite; composition varies, approximately Na(Li,Al)₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Small, dark green-brown, translucent specimen with parallel color bands and vitreous luster. Tourmaline is typically trigonal, Mohs 7–7.5, with poor cleavage and specific gravity around 3.0–3.3; the image alone cannot confirm the species.

Identified October 13, 2026More mineral →

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Physical properties

Formation & geological history

Tourmaline commonly crystallizes in granitic pegmatites and related veins as magma cools; its age depends on the host deposit. Pegmatites occur in Rondônia, but the reported location is only a weak clue.

Uses & applications

Gem-quality tourmaline is cut for jewelry; lesser material is collected as mineral specimens. This small piece appears more suited to collecting than jewelry.

Geological facts

Tourmaline crystals often grow as elongated prisms and can show striking color zoning; parallel bands are a useful clue, though not diagnostic.

Field identification & locations

The apparent zoning and luster favor tourmaline, but a clear view of crystal shape or simple hardness/cleavage tests would help distinguish it from other banded minerals. Avoid destructive tests on a small specimen.