Dravite (Tourmaline) | Gemopedia

Dravite is the dark yellow to brown variety of tourmaline. It is named after a deposit in modern day Slovenia near the Drave river.
Colors
Dark Yellow To Brownish Black

Dravite (Tourmaline) Classification

Common Name

Dravite (Tourmaline)

Species

Dravite

Variety

Colors

Dark Yellow To Brownish Black

Alternate Names

Gemstone Groups

Tourmaline

Key Separations

appearance, refractive index and high birefringence; then optic figure, pleochroism and specific gravity

Comments

Named for the river Drau in the Republic of Slovenia.Dark stones might have a birefringence as high as 0.040.Pyroelectric: development of opposite charges at the ends of a tourmaline crystal due to change in temperature. Piezoelectric: development of opposite charges at the ends of a tourmaline crystal when placed under stress.

Dravite (Tourmaline) Optical Properties

Transparency

Transparent - Translucent

Refractive Index

1.614-1.666

Birefringence

0.014-0.032

Optic Character

Uniaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert to weak
LWUV: Inert to weak

CCF Reaction

Pleochroism

Dichroic, strong pale yellow to colorless and yellow, green, or brown

Dispersion

Strength: moderate fire Value: 0.017

Comments

Dravite (Tourmaline) Chemistry & Crystallography

Chemical Name

Sodium magnesium boro-aluminum silicate hydroxide

Chemical Formula

Na(Mg3)Al6(Si6O18)(BO3)3(OH)3(OH)

Synthesis

Crystal System

Trigonal

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Dravite (Tourmaline) Characteristic Physical Properties

Hardness

7

Streak

White

Specific Gravity

3-3.26 Typical:3.06

Toughness

Good

Inclusions

Dravite is a Type II clarity stone. Stones might have liquid and gas inclusions that are long and thin, reflective gas-filled fractures and color zoning.

Luster

Vitreous

Stability

Very Good

Fracture

Conchoidal, Uneven

Cleavage

Poor, in two directions

Comments

JTV on Google+
0 Items
My Wish List
Close
Item
Description
Qty.
Price


Estimated Order Total:
0
Total Due Today:
0
Close
Item
Description
Qty.
Price


Page of 1