Day #81 Deskcrop: Tigerton Wiborgite Porphyry

The ~1475 Ma Tigerton Wiborgite Porphyry outcrops near the Embarrass River in the Wolf River Batholith of east-central Wisconsin. This rock has a phaneritic porphyritic texture – rapakivi textured K-feldspar megacrysts in a phaneritic granitic groundmass. I wish I had a stained slab to show you the dramatic sodic rims on these big K-spars, but I’m afraid you’ll have to use your imagination.

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Tigerton Wiborgite Porphyry

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