General formula of orthopyroxene: (Mg,Fe)2[Si2O6]
Enstatite-Ferrosilite
nα=1.650- 1.768
nβ=1.653 - 1.770
nγ=1.658 - 1.788
δ=0.007 - 0.020
2V:
+(54-84)° - Enstatite
+84 - (-75)° - 'Bronzite'
- (75-55)° - 'Hypersthene'
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| Relationship between 2V angle and composition of orthopyroxene. |
Thin section pictures: |
| Orthopyroxene 'hypersthene'' (2V=-60°) in gabbro-diorite, Spencer Butte, Oregon |
seems there is a mistake in the figure. b should be parallel to beta and a to alpha. Anyway i found on Deer howie and zussmann that n_gamma and n_alpha varies lineary between the two extremes, what about n_beta?
ReplyDeletesorry, seems to be correct accordign the deer howie and zussmann
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