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Igneous rock, with gray groundmass and white phenocrysts marked. Orthoclase phenocrysts within a finer-grained matrix of a granite porphyry. The matrix or groundmass of a rock is the finer-grained mass of material in which larger grains, crystals, or clasts are embedded.
Phaneritic (phaner = visible) textures are typical of intrusive igneous rocks, these rocks crystallized slowly below Earth's surface. As magma cools slowly the minerals have time to grow and form large crystals. The minerals in a phaneritic igneous rock are sufficiently large to see each individual crystal with the naked eye.
Associated rock type; With what rock type and/or other minerals is this mineral found? Degree of metamorphism and alteration; Mineral shape, properties or form been altered. Lattice structure and geochemistry; Signature chemical elements and bonds of the mineral. For example, is the mineral hydrous like mica or non hydrous like Jadeite.
According to W.A. Tarr (1938) the primary mineral deposits are the result of direct magmatic action; he states that the splitting of magmas results in the basic igneous rocks and their accompanying group of accessory minerals formed by the first crystallization in the magma, on the one hand, and in the acidic igneous rocks and a second group of ...
Identifying whether a rock is a cumulate or not is crucial for understanding if it can be modelled back to a primary melt or a primitive melt, and identifying whether the magma has dropped out cumulate minerals is equally important even for rocks which carry no phenocrysts.
The minerals present in the rock often do not reflect conditions of chemical equilibrium, and the textures produced by dynamic metamorphism are more significant than the mineral makeup. [ 65 ] There are three deformation mechanisms by which rock is mechanically deformed.
Solidified lava flow in Hawaii Sedimentary layers in Badlands National Park, South Dakota Metamorphic rock, Nunavut, Canada. Geology (from Ancient Greek γῆ (gê) 'earth' and λoγία () 'study of, discourse') [1] [2] is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. [3]
Pyrrhotite, and other opaque minerals can be identified optically using a reflected light ore microscope. [19] The following optical properties [20] are representative of polished/puck sections using ore microscopy: Photomicrograph of pyrrhotite under reflected light appearing as cream-pink to beige irregular anhedral masses (5x/0.12 POL).