29 March 2019

OCTOBER BIRTHSTONES – TOURMALINE  have a wide variety of exciting colors with one of the widest color ranges of any gem. Tourmaline’s colors have many different causes. It’s generally agreed that traces of iron, and possibly titanium, induce green and blue colors. Manganese produces reds and pinks, and possibly yellows. Some pink and yellow tourmalines might owe their hues to color centers caused by radiation, which can be natural or laboratory-induced.
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 harness: 7 to 7.5;
COLOR: Tourmaline’s rainbow colors have a wide range of color intensity and tone;
CLARITY: Pink to red tourmaline often has more visible inclusions than green to blue varieties;
CUT: Tourmaline crystals are often long, leading cutters to cut slender finished stones;
CARAT WEIGHT: Tourmalines come in all shapes and sizes. The value change for size varies with the variety~29.jpg

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