from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun A fine-grained light gray volcanic rock consisting primarily of quartz, plagioclase feldspar, and potassium feldspar, and also containing biotite, hornblende, or pyroxene.
from The Century Dictionary.
- noun A name first used by Fr. Von Hauer and Stache, in 1863, in describing the geology of Transylvania, to include the varieties of greenstone-trachyte which contain quartz.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun geology An
igneous, volcanic rockwith a high ironcontent.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun a grey volcanic rock containing plagioclase and quartz and other crystalline minerals
from The American Heritage® Dictionary of the English Language, 4th Edition
from Wiktionary, Creative Commons Attribution/Share-Alike License
Basalt magma typically generates very little ash compared to other types (andesite, dacite, and rhyolite).
For example, volcanic eruptions range from (1) effusion of lava fountains and flows with very little ash erupted, typical of basaltic magma eruptions; to (2) extremely explosive eruptions that inject large quantities of ash high into the stratosphere, typical of rhyolite and dacite magmatic eruptions.
An intrusive complex of dacite with sedimentary and metamorphic rocks of Palaeozoic age comprise the predominant rock forms.
Rocks formed from felsic magma include granite, granodiorite, dacite, and rhyolite.
Rhyolite and dacite are produced from continental lava flows that solidify quickly.
At Goldfield, Nevada, native gold is found in surface igneous flows of a dacite type, which have undergone extensive hydrothermal alterations characterized by the development of alunite (a potassium-aluminum sulphate), quartz, and pyrite.
They cover up to 100 miles of trail beneath silver wattle and broad-leaf peppermint trees, scramble across crumbly dacite rocks.
Montierth explained that Tumtum and St. Helens were both formed out of thick, gooey lava that doesn't travel far as it cools into dacite rock.
The 2009 drilling program identified widespread gold mineralization associated with mineralized and altered dacite porphyry and adjacent sedimentary and volcanic rocks, drill hole DDH09-014 revealed gold mineralization of 111 meters grading up to 7.28 grams/tonne.
Dacite lava hand sample, with abundant amphibole and plagioclase feldspar. magma mixing or crustal assimilation (by another magma) to form the dacite.