Day #48 Deskcrop: Hornblende-rich Pegmatite

Part of my Ph.D. field work brought me to the Eagle Rest Peak intrusive suite located in the San Emigdio Mountains of the Sierran Tail, southwest of Bakersfield, California. Much of this Jurassic intrusion here is gabbroic, with minor ultramafic units, and a fair amount of tonalitic rocks, as well. The deskcrop below is in no way representative of the complex as a whole – to the best of my recollection it’s the only pegmatitic rock I collected there, but it quickly became a favorite teaching piece for its large, well formed hornblende crystals. It’s hard to illustrate the excellent 56o-124o cleavages that these crystals show in a photograph, but you can see a hint of it in the pseudo-diamond cross section of the crystal near the center of the rock.

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Hornblende-rich Pegmatite

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