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Tourmaline

JewelryWiki Editorial·3 sources·Reviewed 2026-07-31
Tourmaline specimen
Tourmaline specimen. Robert M. Lavinsky, CC BY-SA 3.0 · Wikimedia Commons

An unusually wide specific-gravity range, reflecting how variable the group's chemistry is.

Properties

PropertyValueAuthority
Refractive index1.614–1.666 [1]—
Specific gravity2.82–3.90 [1]—
Crystal systemHexagonal [3]—
Birthstone monthOctober — shares October with opal. [2]—

Sources

  1. International Gem Society — reference charts (Mohs hardness, specific gravity, refractive index) — International Gem Society (IGS reference charts)
  2. Jewelers of America — Birthstones — Jewelers of America (Jewelers of America, Birthstones)
  3. Wikipedia — mineral article infoboxes (crystal system) — Wikipedia contributors (Wikipedia mineral infoboxes)