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Microtektites, the fourth group of tektites, are less than 1 mm in size. They exhibit a variety of shapes ranging from spherical to dumbbell, disc, oval, and teardrop. Their colors range from colorless and transparent to yellowish and pale brown. They frequently contain bubbles and lechatelierite inclusions.
In its non-geologic, traditional use, the term porphyry usually refers to the purple-red form of this stone, valued for its appearance, but other colours of decorative porphyry are also used such as "green", "black" and "grey". [1] [2] The term porphyry is from the Ancient Greek πορφύρα (porphyra), meaning "purple".
The biotites in I-type granites are greener in general than those in S-type, both in hand sample and in plane polarized light. More mafic composition granites, those with a higher color index, contain more hornblende and biotite. [1] Hornblende is a typical I-type granite mineral which never occurs in S-type granite.
Monzogranite – Biotite granite rocks that are considered to be the final fractionation product of magma – A silica-undersaturated granite with <5% normative quartz; Monzonite – Igneous intrusive rock with low quartz and equal plagioclase and alkali feldspar – a plutonic rock with <5% normative quartz
Porphyritic texture in a granite. This is an intrusive porphyritic rock. The white, square feldspar phenocrysts are much larger than crystals in the surrounding matrix; eastern Sierra Nevada, Rock Creek Canyon, California. A porphyritic volcanic sand grain, as seen under the petrographic microscope. The large grain in the middle is of a much ...
Decomposed granite is a kind of granite rock that is weathered to the point that the parent material readily fractures into smaller pieces of weaker rock. Further weathering yields material that easily crumbles into mixtures of gravel -sized particles known as grus that further may break down to produce a mixture of clay and silica sand or silt ...
The granite is mined at the E. L. Smith Quarry, the world's largest "deep hole" granite quarry, owned by the Rock of Ages Corporation. All of the stones in the Hope Cemetery in neighboring city of Barre are made with Barre granite. [3] "Barre Gray" granite is sought after worldwide for its fine grain, even texture, and superior weather resistance.
Color: White, grey, greyish yellow, yellowish, tan, salmon-pink, bluish green, green. Crystal habit: Can be anhedral or euhedral. Grains are commonly elongate with a tabular appearance. May contain lamellae which formed from exsolved albite. Twinning: Typically displays albite twinning and pericline twinning.