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The name diorite (from Ancient Greek διορίζειν, "to distinguish") was first applied to the rock by René Just Haüy [10] on account of its characteristic, easily identifiable large crystals of hornblende. [4] Dioritoids form a family of rock types similar to diorite, such as monzodiorite, quartz diorite, or nepheline-bearing diorite ...
Anorthosites are of enormous geologic interest, because it is still not fully understood how they form. Most models involve separating plagioclase crystals based on their density. Plagioclase crystals are usually less dense than magma; so, as plagioclase crystallizes in a magma chamber, the plagioclase crystals float to the top, concentrating ...
The individual crystals in an aphanitic igneous rock are not distinguishable to the naked eye. Examples of aphanitic igneous rock include basalt , andesite , and rhyolite . Glassy or vitreous textures occur during some volcanic eruptions when the lava is quenched so rapidly that crystallization cannot occur.
Soil conditions produce uniform or gradual color changes, while reducing environments result in disrupted color flow with complex, mottled patterns and points of color concentration. Sometimes, a distinct change in color within a soil profile indicates a change in the soil parent material or mineral origin.
The above geochemical classification must be the essentially unaltered magma chemistry and not the result of crystal accumulation (as in peridotite). Through a typical komatiite flow sequence the chemistry of the rock will change according to the internal fractionation which occurs during eruption.
The name comes from two related rocks to which granodiorite is an intermediate: granite and diorite. The gran-root comes from the Latin grānum for "grain", an English language derivative. Diorite is named after the contrasting colors of the rock.
Amphibolite from Cape Cod, Massachusetts Garnet bearing amphibolite from Val di Fleres, Italy. Amphibolite (/ æ m ˈ f ɪ b ə l aɪ t /) is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz.
In hand specimen, many of the hornblende and biotite dacites are grey or pale brown and yellow rocks with white feldspars, and black crystals of biotite and hornblende. Other dacites, especially pyroxene-bearing dacites, are darker colored. [4] In thin section, dacites may have an aphanitic to porphyritic texture.