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Slate is a fine-grained, ... This is in contrast to the silky cleaved surfaces of phyllite, ... These are typically less than 100 μm (micron) ...
Phyllite Photomicrograph of thin section of phyllite (in cross polarised light) Fractured Duke stone showing phyllitic texture Phyllite. Phyllite (/ ˈ f ɪ l aɪ t / FIL-yte) is a type of foliated metamorphic rock formed from slate that is further metamorphosed so that very fine grained white mica achieves a preferred orientation. [1]
Rocks exhibiting foliation include the standard sequence formed by the prograde metamorphism of mudrocks; slate, phyllite, schist and gneiss. The slatey cleavage typical of slate is due to the preferred orientation of microscopic phyllosilicate crystals. In gneiss, the foliation is more typically represented by compositional banding due to ...
These show the most well-developed schistosity, defined as the extent to which platy minerals are present and are aligned in a single direction, so that the rock easily splits into plates less than a centimeter (0.4 inches) thick. [24] Gneisses, which are more coarse grained and show thicker foliation than schists, with layers over 5mm thick. [23]
Clay minerals are very common in soils, in fine-grained sedimentary rocks such as shale, mudstone, and siltstone and in fine-grained metamorphic slate and phyllite. [ 9 ] Given the requirement of water, clay minerals are relatively rare in the Solar System , though they occur extensively on Earth where water has interacted with other minerals ...
Slate in turn is converted to phyllite, which is fine-grained and found in areas of low grade metamorphism. Schist is medium to coarse-grained and found in areas of medium grade metamorphism. High-grade metamorphism transforms the rock to gneiss, which is coarse to very coarse-grained. [37]
The formation was originally designated as the Hondo Slate by Evan Just in his 1937 survey of pegmatites in northern New Mexico. [5] However, this name conflicted with other unit names, and it was renamed the Pilar Phyllite Member of the Ortega Formation by Arthur Montgomery in 1953 [6] Bauer and Williams promoted it to formation rank within the Vadito Group in their sweeping revision of the ...
Foliated metaconglomerate is created under the same metamorphic conditions that produce slate or phyllite, but with the parent rock being conglomerate, rather than clay. [2] The metaconglomerates of the Jack Hills of Western Australia are the source rocks for much of the detrital zircons that have been dated to be as old as 4.4 billion years.