Rating
Name	Tourmaline (thin section)
Type	Mineral
Cleavage	Cleavage not visible in thin section; Grains are commonly fractured
Colour and Pleochroism	Essentially any color is possible, may also be colorless; Colored varieties are strongly pleochroic
Relief	Moderate to high positive relief
Form	occurs as euhedral to subhedral columnar prisms with triangular cross section; Hexagonal cross section possible but rare
Optical Orientation	Parallel extinction, length fast
Twinning	None
Birefringence, δ	δ = 0.015 - 0.035; Maximum interference colors upper second order, often masked by mineral's strong color
Optical Character	Uniaxial (-)
2V	n/a
Key Characteristics	The mineral's high relief, strong pleochroism, form and uniaxial character are diagnostic
Photograph Comments	pic 1(left): plane polarized light, magnification 40x, arrow refers to triangular cross section; pic 2(right): cross polarized light, magnification 40x, arrow refers to mineral grain displaying parallel extinction
Subject	Minerals; Rocks; Identification photographs; Geology;
Date	2009
Format	image/jpeg
Identifier	2009-rm-0015
Collection Title	Rock and Mineral Samples
Repository	AU Digital Library
Rights	Subject to the Copyright Act

Tourmaline (thin section)

Description