These six minerals are mounted on one slide to show comparative relief.
A continuous foliation for this sample is defined by aligned hornblende, micas, elongate quartz grains and granular aggregates of epidote and clinozoisite. Quartz is either equant or elongate with a granular texture. The hornblende phase is generally subhedral in shape, as are biotite crystals, which appear to be pseudomorphing an earlier mineral phase as evidenced by abundant inclusions. Radiation halos can be found in this sample though their occurrance is rare.
A very poorly sorted rock with variably sized and angular quartz and feldspar pieces (both plagioclase and orthoclase; some fresh, others sericitized) set in a finer-grained matrix of chlorite, sericite, carbonate, silky quartz, leucoxene, magnetite and pyrite. Matrix chlorite corrodes quartz grains marginally. A few microfragments of rock (quartzite, granite, gneiss) also are present. Accessory detritals include muscovite, sphene, tourmaline and epidote. Most of the quartz pieces are markedly undulatory. A very low degree of incipient metamorphism is indicated by abundant secondary epidote in the matrix which also locally contains minute platelets of stilpnomelane.
This sample is an almost monomineralic hornblende amphibolite with trace occurances of poikiloblastic orthoclase and biotite. Biotite growth concentrates along the margins of a high relief, clear mineral with fifth-order birefringence, extreme enough that the inclusions appear to not go extinct. Rarely are radiaiton halos observed in hornblende crystals.
Wards' samples with oriented crystals to show varying 2V angles.
This medium-grained allotriomorphic diorite is dominated by plagioclase, much of which is concentrically zoned and larger in size than most other phases in the sample. Clusters of the ferromagnesian phases appear to be pseudomorphing a previous, rectangular, phenocrystic phase.
Highly sericitized subhedral feldspars comprise the bulk of this thin section. Anhedral quartz fills in interstices between feldspar grains. Chlorite pseudomorphism of hornblende is prevalent and biotite alteration, chloritization, and embayment indicates of it too, was out of equilibrium with the melt. Euhedral titanite is found throughout.
In thin section, this flow-banded aphanitic rock displays a few fractured and embayed plagioclase and clinopyroxene phenocrysts in a groundmass dominated by aligned microlites of the same two phases. One or two phenocrysts of orthoclase are also present. The microlites define a trachytic texture, which is observable in handsample as flow bands.
Although stored with a series of amphibolites, this hornblende-bearing granodiorite preserves more igneous textures than metamorphic. This hypidoimorphic sample consists of equigranular feldspars, randomly oriented, euhedral biotites, and rather anhedral hornblendes grains. Small, rounded, colorless but dusty crystals of titanite are distrubuted throughout the specimen.
This amphibolite has a strong, continuous foliation defined by the alignment of hornblende. Elongate, granular aggregates of epidote are present.