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Tourmaline (/ˈtʊərməlɪn, -ˌliːn/ ⓘ TOOR-mə-lin, -leen) is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a wide variety of colors.
History, Species and varieties & Physical properties
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| Subject | Predicate | Object | Confidence | Src |
|---|---|---|---|---|
| Tourmaline | Absorption spectra | Strong narrow band at 498 nm, and almost complete absorption of red down to 640 nm in blue and green stones; red and pink stones show lines at 458 and 451 nm, as well as a broad… | 1.00 | infobox |
| Tourmaline | Birefringence | −0.018 to −0.040; typically about −0.020 but in dark stones it may reach −0.040 | 1.00 | infobox |
| Tourmaline | Category | Cyclosilicate | 1.00 | infobox |
| Tourmaline | Cleavage | Indistinct | 1.00 | infobox |
| Tourmaline | Color | Most commonly black, but can range from colorless to brown, red, orange, yellow, green, blue, violet, pink, or hues in-between. It can also be bi-colored, or even tri-colored. R… | 1.00 | infobox |
| Tourmaline | Crystal class | Ditrigonal pyramidal (3m) H-M symbol: (3m) | 1.00 | infobox |
| Tourmaline | Crystal habit | Parallel and elongated; acicular prisms, sometimes radiating; massive; scattered grains (in granite) | 1.00 | infobox |
| Tourmaline | Crystal system | Trigonal | 1.00 | infobox |
| Tourmaline | Density | 2.82–3.32 | 1.00 | infobox |
| Tourmaline | Diaphaneity | Translucent to opaque | 1.00 | infobox |
| Tourmaline | Dispersion | 0.017 | 1.00 | infobox |
| Tourmaline | Formula | .mw-parser-output .template-chem2-su{display:inline-block;font-size:80%;line-height:1;vertical-align:-0.35em}.mw-parser-output .template-chem2-su>span{display:block;text-align:l… | 1.00 | infobox |
| Tourmaline | Fracture | Uneven, small conchoidal | 1.00 | infobox |
| Tourmaline | IMA symbol | Tur | 1.00 | infobox |
| Tourmaline | Luster | Vitreous, sometimes resinous | 1.00 | infobox |
| Tourmaline | Mohs scale hardness | 7.0–7.5 | 1.00 | infobox |
| Tourmaline | Optical properties | Double-refractive, uniaxial negative | 1.00 | infobox |
| Tourmaline | Pleochroism | Typically moderate to strong | 1.00 | infobox |
| Tourmaline | Pleochroism | Red: definite; dark red, light red | 1.00 | infobox |
| Tourmaline | Pleochroism | Green: strong; dark green, yellow-green | 1.00 | infobox |
| Tourmaline | Pleochroism | Brown: definite; dark brown, light brown | 1.00 | infobox |
| Tourmaline | Pleochroism | Blue: strong; dark blue, light blue | 1.00 | infobox |
| Tourmaline | Polish luster | Vitreous | 1.00 | infobox |
| Tourmaline | Refractive index | nω = 1.635–1.675 nε = 1.610–1.650 | 1.00 | infobox |
| Tourmaline | Space group | R3m (no. 160) | 1.00 | infobox |
| Tourmaline | Specific gravity | 3.06+0.20–0.06 | 1.00 | infobox |
| Tourmaline | Streak | White | 1.00 | infobox |
| Tourmaline | Tenacity | Brittle | 1.00 | infobox |
| Tourmaline | Ultraviolet fluorescence | Pink stones; inert to very weak red to violet in long and short wave | 1.00 | infobox |
| Tourmaline | is a | only blue gemstone of any kind that will show a drag response when a neodymium magnet is applied | 0.90 | text |
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