Dacite
A species of Igneous Scientific name : Dacite RockType : Igneous
Dacite, A species of Igneous
Scientific name: Dacite
RockType: Igneous
Content
Description People often ask General Info
Photo By James St. John , used under CC-BY-2.0 /Cropped and compressed from original 
Description
Dacite is a relatively common volcanic rock that can be found in several different hues. Ancient people sometimes used dacite in place of flint to create spears or arrowheads. The rock’s name is derived from “Dacia”, the ancient Roman province near modern Romania, where it was first described. Today, the stone is crushed and used as filler in construction projects.
Physical Properties
Colors
Bluish-Grey, Brown, Light to Dark Grey
Texture
AphaniticPorphyritic
Chemical Properties
Silica (SiO2) Content
63%-69%
People often ask
General Info
Usage
Dacite can be used as a filler rock when paving and constructing roads, though it is not a popular choice due to its high silica content that may easily damage or weather. It may also be used for decorative purposes or stone carvings.
Composition
Dacite consists mostly of plagioclase feldspar with biotite, hornblende, and pyroxene (augite and/or enstatite). It has quartz as some rounded, corroded phenocrysts, or as an element of the ground-mass. 
Formation
Dacite usually forms as an intrusive rock such as a dike or sill. Examples of this type of dacite outcrop are found in northwestern Montana and northeastern Bulgaria. Nevertheless, because of the moderately high silica content, dacitic magma is quite viscous and therefore prone to explosive eruption. A notorious example of this is Mount St. Helens in which dacite domes formed from previous eruptions. Pyroclastic flows may also be of dacitic composition as is the case with the Fish Canyon Tuff of La Garita Caldera.
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