Minerals - Descriptions, photos, articles, properties and uses for common minerals.
The specimen shown is about two inches five centimeters across. What are Igneous Rocks? Igneous rocks are formed from the solidification of molten rock material. There are two basic types. Intrusive igneous rocks crystallize below Earth's surface, and the slow cooling that occurs there allows large crystals to form.
Examples of intrusive igneous rocks are dioritegabbrogranitepegmatiteand peridotite. Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals.
Some cool so quickly that they form an amorphous glass. These rocks include andesitebasaltdaciteobsidianpumicerhyolitescoriaand tuff.
Pictures and brief descriptions of some common igneous rock types are shown on this page. Dacite is a fine-grained, extrusive igneous rock that is usually light in color. It has a composition that is intermediate between rhyolite and andesite. The specimen shown is about four inches ten centimeters across.
Basalt is a fine-grained, dark-colored extrusive igneous rock composed mainly of plagioclase and pyroxene. Diorite is a coarse-grained, intrusive igneous rock that contains a mixture of feldsparpyroxene, hornblendeand sometimes quartz. The specimen shown above is about two inches five centimeters across.
Granite is a coarse-grained, light-colored, intrusive igneous rock that contains mainly quartzfeldspar, and mica minerals. The specimen above is about two inches five centimeters across. Gabbro is a coarse-grained, dark-colored, intrusive igneous rock that contains feldspar, pyroxene, and sometimes olivine.
Pegmatite is a light-colored, extremely coarse-grained intrusive igneous rock. It forms near the margins of a magma chamber during the final phases of magma chamber crystallization.
It often contains rare minerals that are not found in other parts of the magma chamber. Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form. Pumice is a light-colored vesicular igneous rock.
It forms through very rapid solidification of a melt. The vesicular texture is a result of gas trapped in the melt at the time of solidification. Peridotite is a coarse-grained intrusive igneous rock that is composed almost entirely of olivine.
It may contain small amounts of amphibole, feldspar, quartzor pyroxene. Fire Opal is sometimes found filling cavities in rhyolite. Long after the rhyolite has cooled, silica-rich ground water moves through the rock, sometimes depositing gems like opalred beryltopazjasper, or agate in the cavities of the rock.
This is one of many excellent geological photographs generously shared through a Creative Commons License by Didier Descouens. Rhyolite is a light-colored, fine-grained, extrusive igneous rock that typically contains quartz and feldspar minerals.
Welded Tuff is a rock that is composed of materials that were ejected from a volcano, fell to Earth, and then lithified into a rock. It is usually composed mainly of volcanic ash and sometimes contains larger size particles such as cinders.
Scoria is a dark-colored, vesicular, extrusive igneous rock. The vesicles are a result of trapped gas within the melt at the time of solidification.Igneous rocks are one of the three major rock types and are basically rocks that solidified from vilakamelia.com is the term for liquid or melted rock and is usually quite hot.
After all, the term igneous comes from the Latin word for "of fire". Most people have seen pictures or video of magma that flows out of a volcano.
When magma flows onto the . Intrusive rocks crystallize and harden beneath the Earth's surface in rock formations include plutons, batholiths, dikes, sills, laccoliths, and volcanic necks. Colorado Geology Photojournals A Tribute to Colorado's Physical Past and Present Right: Trees and snow mark major Laramide uplifts in green and white while salmon pink marks the Colorado Plateau in this true-color satellite image of Colorado and surrounding states, courtesy NASA, ^Visible Earth.
Intrusive rock, also called plutonic rock, igneous rock formed from magma forced into older rocks at depths within the Earth’s crust, which then slowly solidifies below the Earth’s surface, though it may later be exposed by vilakamelia.coms intrusions form a variety of rock types.
See also extrusive rock. Photographs and information for a large collection of igneous, metamorphic and sedimentary rocks. vilakamelia.com Rockhounding Wisconsin. Wisconsin is a good state for rockhounding.