| Text Description: |
Blocky and platy outcrop of silicic material that appears to have a vertical contact with andesite to the west on the west side of Sheep Lake. Fine grained, holocrystalline, porphyritic with a matrix of cryptocrystalline material, plagioclase and opaque. Plagioclase phenocrysts are up to 1.0 mm and most grains are small laths; larger grains occasionally display oscillatory zoning and/or sieve textured zones. There is a dehydrated phase, amphibole?, that now consists of fine masses of opaque. Orthopyroxene phenocrysts up to 0.75 mm. Opaque phenocrysts up to 0.45 mm. 91.2% matrix, 8.5% plagioclase, 0.2% opaque, 0.1% altered phase. |