Elbaite

1364

mindat:1:1:1364:8

db0ae747-1af0-413f-8d08-282bf1f135af

Approved, 'Grandfathered' (first described prior to 1959)

9.CK.05

9 : SILICATES (Germanates)
C : Cyclosilicates
K : [Si₆O₁₈]₁₂- 6-membered single rings, with insular complex anions

61.3.1.10

61.3.1.8

61 : CYCLOSILICATES Six-Membered Rings
3 : Six-Membered Rings with borate groups

17.5.5

17 : Silicates Containing other Anions
5 : Borosilicates

Vitreous, Resinous

Transparent, Translucent

Green, blue-green, blue, red to pink, orange, yellow, colourless

The isomorphous substitution of ions forms the different colors of tourmalines. The cations in the structure (such as Fe, Mn, Cr, etc.) exist in a wide range of isomorphous substitutions, which gives tourmaline a very rich color. There are no or very few transition metal ions in colorless tourmaline. The red hue of tourmaline is attributed to the d-d transition of octahedral Mn3+, Mn2+, or Mn2+-Mn3+ intervalence charge transfer (IVCT) in its crystal structure. The deep blue color is due to Fe2+, Fe3+, and Mn3+. The “neon” blue color of Paraíba tourmaline is attributed to Cu2+ and Mn3+. The yellow color could be associated with both the Fe2+-Ti4+ and Fe2+-Fe3+ intervalence charge transfers. Regarding the color genesis of green tourmalines, many previous experimental studies have shown that it is due to the isomorphous substitution of transition metal ions, such as Cr, V, and Fe, at the Y or Z position in its structure. It has also been shown that the green color of tourmaline is due to defects in the crystal structure of tourmaline.[[1]] The chromogenic components iron and manganese were found in the green elbaites; however, the bivariate correlation analysis indicated that the Mn content had no impact on the color, whereas the Fe content significantly affected both the lightness and the hue of green elbaites. The primary factors influencing the color of tourmaline were the absorption band at 720 nm caused by the Fe2+ d-d transitions and the 300 to 400 nm wide absorption edge extending to the visible range due to the O2−-Fe3+ charge transfer. Infrared spectroscopy indicated that the color of tourmalines was also influenced by their structure. As the degree of Y and Z octahedral distortion in the tourmaline lattice increased, the lightness of the tourmaline decreased and its color deepened.[[1]]

White

7½ on Mohs scale

Brittle

Poor/Indistinct
on {1120} and {1011}

Irregular/Uneven, Conchoidal

2.9 - 3.1 g/cm³ (Measured)    3.069 g/cm³ (Calculated)

Uniaxial (-)

n_ω = 1.633 - 1.651 n_ε = 1.615 - 1.630

δ = 0.018 - 0.021

Moderate

Visible

O- Pink, pale green, pale to deep blue
E- Colourless, yellow, olive-green, purplish

Al, B, H, Li, Na, O, Si - search for minerals with similar chemistry

Fe,Mn,Cu,Ti,Ca,F

Trigonal

3m - Ditrigonal Pyramidal

R3m

a = 15.86(6) Å, c = 7.11(2) Å

a:c = 1 : 0.448

1,548.84 ų (Calculated from Unit Cell)

3

Prismatic to acicular

Rare on {1011}{4041}

Radiation - Copper Kα

Data Set: Minas Gerais, Brazil 1285 White Queen mine, Pala, San Diego County, California, USA 1785 Mount Begbie, Revelstoke, British Columbia, Canada 2102

Data courtesy of RRUFF project at University of Arizona, used with permission.

Mt. Apatite, Maine, USA. ICDD 26-964.

Lithium-rich granitic pegmatites, metamorphic rocks and high temperature hydrothermal veins.

ⓘ Fonte del Prete, San Piero in Campo, Campo nell'Elba, Livorno Province, Tuscany, Italy

No designated type material.

blue shortwave-excited luminescence excited by SW UV caused by titanate groups (TiO₆)

Pyroelectric, piezoelectric

No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Gemstone

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