Hornblende porphyrite - Valparaiso
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Fact sheet
Description: 

Darwin wrote "Blackish grey sonorous, even semi-conchoidal porphyry, with many acicular crystals of glassy feldspar & common do. & hornblende; forming part of contemporaneous vein (it has character of phonolite)"

Euhedral microphenocrysts of plagioclase feldspar and brown hornblende are the major constituents of this rock. They are accompanied by large xenolithic fragments of green amphibole (actinolite) and quartz. The groundmass contains all the previously mentioned species and is peppered with tiny (black) iron oxide crystals. Collected June-July 1834.

In Place
In Time
Location description: 
Valparaiso, Chile
Accuracy:
Location precision: 
Moderate
Timescale:
Not known
Ma = Millions of years ago
In Focus
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Type:
Type: 
igneous
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