Although commonly light yellow-green in thin section, it may be colorless. 92; Sub-greenschist facies metamorphism in Keweenawan ... Subhedral epidote grain in greenstone 08/28 - 09/04 (3) Garnet micaschist The word schist is derived from the Greek word schízein meaning "to split", which is a reference to the ease with which schists can be split along the plane in which the platy minerals lie. On this PT grid, the Mirado rocks will plot in lower greenschist fields. 1, full thin section in cross-pol... Greenschist, No. Identification of minerals in thin sections can be aided by studying as many images of a mineral as possible. Documentation of the hydrothermal alteration assemblages The 11 Mirado polished thin sections contain two predominant alteration assemblages which are From the Achean shield greenschists, this rock contains mainly actinolite, bright green in hand sample, showing fine twinning and some dissolution texture, also muscovite and, … The large black grain is the garnet, the red elongate grains are mica flakes. Euhedral crystals are more common in volcanic rocks and sections usually are equidimensional, or slighly elongate parallel to c with six or eight sides. This must be the most attractive Malaysian rock in thin section, because of the blue–violet pleochroism of glaucophane and the yellow–pink pleochroism of piedmontite, set in a mosaic of normal quartz. The same mineral can look quite different in different rocks. Petrology. Actinolite in greenschist; Epidote pleochroism in greenschist; Greenschist, No. A “thin section” of rock is a sample that is mounted to a microscope slide and cut so thin that you can see light through it. The contiguous outcrops of metabasalts (fine-grained amphibolite) also contain small amounts of glaucophane and piedmontite. This assistant is designed to give varying views of the same mineral in differing situations. Garnet mica schist in thin section: This is a microscopic view of a garnet grain that has grown in schist. Thin Section of a Greenschist, XPL. The black, gray, and white grains are mostly silt or smaller size grains of quartz and feldspar. Plane/cross-polarized light, field width is 1.2 mm. Photo Courtesy: Laura: 13. The process of creating a thin section is a blend of artistry, technology and science. Alex Strekeisen - I vetrini della mia fantasia. A schist whose greenish colour is due to the presence of minerals such as actinolite, chlorite and epidote. Relief: Very High – High positive Habit/Form: In most metamorphic and intrusive igneous rocks, olivine tends to form subequant, anhedral grains or aggregates of grains. Its interference colors commonly seem anomalously bright compared to pyroxenes, possibly a result of the high dispersion of the 2V. This is a thin section of a rock from a gold mining site at Kirkland Lake, Ontario, Canada. Greenschists often have some foliation resulting in mineral alignment, especially of chlorite and actinolite. Greenschist, as a rock type, is defined by the presence of the minerals chlorite and actinolite and may contain albite or epidote.Greenschist often has a lepidoblastic, nematoblastic or schistose texture defined primarily by chlorite and actinolite. The general field area is indicated by the red oval and “MPT”. 52 - full thin section in cross-p... Archean greenstone, No. NOR-116