bi color tourmaline 7.07cts - 23x7mm

Tourmaline is the birtstone of October.
The name Tourmaline was derived from the Sinhalese word "Thuramali" or "Thoramalli" which means different colored gemstones. Tourmaline is a chemical combination of boron silicate with aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmalines range in red, green, yellow, pink and blue the basic colors. The other varieties are indicolite, paraiba tourmalines, watermelon tourmalines, chrome tourmalines, bi- color tourmalines. 

In a research article in Wikipedia explaining the variety of tourmalines sorts the tourmalines into 3 basic varieties - dravite the dark brown or vivid honey yellow, schorl is bluish or brownish black and elbaite is categorized as below
Red, Pinkish Red, and purple—rubellite
Dark black
Light blue to bluish green—indicolite
Green—verdelite
Colorless—achroite

gempiece.com has a wide range of natural tourmaline loose gemstones and also deals with custom jewelry for more than a decade. Please feel free to email us if you have any orders and we most warmly welcome you. We serve certificates from Gubelin, GIA- Gemological Institute of America, AIGS- Asian Institute of Gemological Sciences, Tokyo gem lab, GIT, GRS etc. The Hardness is 7.0 - 7.5, the specific gravity is 2.85 to 3.35 and the refractive Index : 1.614 to 1.666.