1554
Francisco Spinoza’s expedition discovers “Brazilian emerald”: the first recorded green tourmaline crystal.
PYROELECTRIC
Tourmaline becomes electrically charged when heated. Also when squeezed: it’s piezoelectric too.
PARAIBA
Brazilian source famous for vivid blue to green tourmalines colored by copper.
FACTS
- Mineral: Tourmaline
- Chemistry:
- Elbaite Na(Li1.5,Al1.5)Al6Si6O18(BO3)3(OH)4
- Dravite NaMg3Al6Si6O18(BO3)3(OH)4
- Liddicoatite Ca(Li2Al)Al6Si6O18(BO3)3(OH)3F
- Chromedravite NaMg3Cr6Si6O18(BO3)3(OH)4
- Color: All colors
- Refractive index: 1.624 to 1.644
- Birefringence: 0.018 to 0.040
- Specific gravity: 3.06 (+0.20, -0.06)
- Mohs Hardness: 7 to 7.5
source:gia.edu
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