Porphyry

Porphyry

Plagioclase gabbro porphyry: golf ball-size "mega" phenocrysts of plagioclase feldspar in a dark green, mafic groundmass. Unique, isolated boulder is a glacially-transported "erratic".

Pyroxene dacite porphyry: dark green pyroxene phenocrysts in an intermediate rock.

Feldspar dacite porphyry: plagioclase feldspar phenocrysts in grey-green intermediate rock.

Feldspar-quartz porphyry.

Quartz-feldspar granite porphyry: clear grey quartz and white feldspar phenocrysts in a felsic rock.