Browse Items (264 total)

Hand Specimen Medium to coarse-grained rock with a granular texture. White feldspar laths 2-4 mm long are clearly visible. Other phases: pink feldspar, black biotite mica, black hornblende amphibole and pale grey quartz. These grains are…

Hand Specimen Superficially specimens “a” and “b” look very different due to their colours. L340a is pale grey, while L340b is dark purple-red. The colour of L340b indicates that it is ferruginous, containing significant quantities of iron…

Hand Specimen Coarse-grained, porphyritic texture. Phenocrysts of pink feldspar, 10-30 mm long, tabular, display clear cleavage planes. Groundmass of coarse-grained white feldspar, pink feldspar, quartz and biotite. Quartz grains…

Hand Specimen This rock has a porphyritic texture. Phenocrysts of white feldspar up to 30mm long are surrounded by a coarse groundmass of quartz, biotite and white feldspar. Thin-section Alkali feldspar (orthoclase) - Grains typically 2-4mm…