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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.
Diorite was also used for stone vases by Bronze Age craftspeople, who developed considerable skill at polishing diorite and other stones. [38] The Egyptians had become skilled at shaping diorite and other hard stones by 4000 BCE. [39] A large diorite stela in the Louvre Museum dating to 1700 BCE is inscribed with the Code of Hammurabi. [40]
Hornblende diorite from the Henry Mountains, Utah, US. Hornblende is a common constituent of many igneous and metamorphic rocks such as granite, syenite, diorite, gabbro, basalt, andesite, gneiss, and schist. It crystallizes in preference to pyroxene minerals from cooler magma that is richer in silica and water. [13]
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Porphyry – Textural form of igneous rock with large grained crystals in a fine matrix; Pumice – Extremely vesicular volcanic rock, typically light-colored; Pyroxenite – Igneous rock - a coarse grained plutonic rock composed of >90% pyroxene; Quartz diorite – Igneous, plutonic rock – A diorite with >5% modal quartz
Napoleonite is a variety of diorite which is characterized by orbicular structure. The grey matrix of the stone has the normal appearance of a diorite, but contains many rounded lumps 1 or 2 inches in diameter, which show concentric zones of light and dark colors.
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.
The hornblende and biotite are brown or greenish-brown, and as a rule their crystals even when small are very perfect and give the thin section views an easily recognizable character. Green hornblende occurs in some of these rocks. Augite exists as euhedral crystals of pale green color, often zonal and readily weathering.