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Tourmaline Specimen 5

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Original price $1,500
Current price $1,300

A very rare color double terminated Pink & Blue Tourmaline Specimen. 

Dimensions (length, width, height): 8.5cm x 5.2cm x 3.7cm

Weight: 205 grams

Origin: Peech Valley. Kunar Afghanistan

Color: Pink & Blue

Double termination.

 

Looks like a Native American head.

 

 

TOURMALINE:

Tourmaline is a crystalline boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classified as a semi-precious stone and the gemstone can be found in a wide variety of colors.

History

Brightly colored Ceylonese gem tourmalines were brought to Europe in great quantities by the Dutch East India Company to satisfy a demand for curiosities and gems. Tourmaline was sometimes called the "Ceylonese Sri Lankan Magnet" because it could attract and then repel hot ashes due to its pyroelectric properties. Tourmalines were used by chemists in the 19th century to polarize light by shining rays onto a cut and polished surface of the gem.

Species and varieties

Schorl species:

Brownish black to black—schorl,

Dravite species: from the Drave district of Carinthia

Dark yellow to brownish black—dravite,

Elbaite species: named after the island of Elba, Italy

Red or pinkish-red—rubellite variety,

Light blue to bluish green—Brazilian indicolite variety (from indigo),

Green—verdelite or Brazilian emerald variety,

Colorless—achroite variety (from the Greek meaning "colorless")

Tourmaline has a variety of colors. Iron-rich tourmalines are usually black to bluish-black to deep brown, while magnesium-rich varieties are brown to yellow, and lithium-rich tourmalines are almost any color: blue, green, red, yellow, pink, etc. Rarely, it is colorless. Bi-colored and multicolored crystals are common, reflecting variations of fluid chemistry during crystallization. Crystals may be green at one end and pink at the other, or green on the outside and pink inside; this type is called watermelon tourmaline. Some forms of tourmaline are dichroic; they change color when viewed from different directions

 

General

Category

Cyclosilicate

Formula

(Ca,K,Na)(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6
(BO3)3(Si,Al,B)6O18(OH,F)4

Crystal system

Trigonal

Crystal class

Ditrigonal pyramidal (3m)
H-M symbol: (3m)

Identification

Color

Most commonly black, but can range from colorless to brown, red, orange, yellow, green, blue, violet, pink, or hues in between; can be bi-colored, or even tri-colored; rarely can be neon green or electric blue

Crystal habit

Parallel and elongated. Acicular prisms, sometimes radiating. Massive. Scattered grains (in granite).

Cleavage

Indistinct

Fracture

Uneven, small conchoidal, brittle

Tenacity

Brittle

Mohs scale hardness

7–7.5

Luster

Vitreous, sometimes resinous

Streak

White

Diaphaneity

Translucent to opaque

Specific gravity

3.06 (+.20 -.06)

Density

2.82–3.32

Polish luster

Vitreous

Optical properties

Double refractive, uniaxial negative

Refractive index

nω=1.635–1.675
nε=1.610–1.650

Birefringence

-0.018 to −0.040; typically about .020 but in dark stones it may reach .040

Pleochroism

·         Typically moderate to strong

·         Red Tourmaline: Definite; dark red, light red

·         Green Tourmaline: Strong; dark green, yellow-green

·         Brown Tourmaline: Definite; dark brown, light brown

·         Blue Tourmaline: Strong; dark blue, light blue

Dispersion

.017

Ultraviolet fluorescence

pink stones—inert to very weak red to violet in long and short wave

Absorption spectra

a strong narrow band at 498 nm, and almost complete absorption of red down to 640nm in blue and green stones; red and pink stones show lines at 458 and 451nm as well as a broad band in the green spectrum