Rating
Name	Hornblende (thin section)
Type	Mineral
Cleavage	Two cleavages intersect at 56 ° and 124 °.
Colour and Pleochroism	Strongly colored green, yellowish-green, brown, bluish-green in thin section; Strong pleochroism; Coloration can be patchy
Relief	Moderate to high positive relief
Form	Usually occurs as bladed or prismatic crystals with a diamond shaped basal cross section which displays two intersecting cleavages at 56 ° and 124 °; Also occurs as anhedral poikiolitic masses.
Optical Orientation	Symmetric extinction in basal sections
Twinning	Simple and lamellar twinning frequent
Birefringence, δ	δ = 0.014 - 0.034; Maximum interference colors generally upper first to lower second order; Interference colors masked by minerals strong color
Optical Character	Biaxial (-) or (+)
2V	2Vx = 35 - 130°
Key Characteristics	Strong coloration and pleochroism, 2 intersecting cleavages, and diamond shaped basal sections are diagnostic
Photograph Comments	pic 1(left): plane polarized light, magnification 40x, note two intersecting cleavages are 56° and 124° in grain in top right of picture; pic 2(right): cross polarized light, magnification 40x
Hand Sample URL	http://digicon.athabascau.ca/u?/RM,77
Subject	Minerals; Rocks; Identification photographs; Geology;
Date	2009
Format	image/jpeg
Identifier	2009-rm-0008
Collection Title	Rock and Mineral Samples
Repository	AU Digital Library
Rights	Subject to the Copyright Act

Hornblende (thin section)

Description