Igneous rock samples used by students at the University of Dayton | Mineral Samples (2024)

FAQs

What are the igneous rocks samples? ›

Examples include granite, gabbro, diabase, diorite, pegmatite, and peridotite.

Therefore, igneous rocks include, but are not limited to, granite, gabbro, pegmatite, basalt, volcanic, breccia, and tuff, hence option B is correct.

There are two basic types: 1) intrusive igneous rocks such as diorite, gabbro, granite and pegmatite that solidify below the Earth's surface; and 2) extrusive igneous rocks such as andesite, basalt, obsidian, pumice, rhyolite and scoria that solidify on or above the Earth's surface.

Igneous rock is composed of crystals or is glassy. It is formed from magma—molten or partially molten rock in the interior of Earth where temperatures are very hot.

Igneous rocks can be divided into four categories based on their chemical composition: felsic, intermediate, mafic, and ultramafic. The diagram of Bowen's reaction series (Figure 7.6) shows that differences in chemical composition correspond to differences in the types of minerals within an igneous rock.

Ultramafic (those with less silica and more iron and magnesium than mafic rocks) plutonic rocks such as dunite, peridotite, and pyroxenite are found in some national parks like Great Smoky Mountains and Kenai Fjords national parks. Ultramafic volcanic rocks are extremely rare, and are not found in any NPS unit.

Human Use of Igneous Rock

One important use is as stone for buildings and statues. Granite is used for both of these purposes and is popular for kitchen countertops. Pumice is commonly used as an abrasive. Pumice is used to smooth skin or scrape up grime around the house.

Identification of igneous rocks involves determining the major minerals (mineralogy) of the rocks and their texture. Determination of the mineralogy is aided by the color of the rock. Remember that ferromagnesian silicates are dark colored minerals and nonferromagnesian minerals are light in color.

Granite is used extensively in building materials and making statues. Perhaps you have used a pumice stone to smooth your skin or to do jobs around the house. Pumice is another example of an igneous rock (Figure 4.2). Pumice is used to make stone-washed denim jeans!

Granite: the most common igneous plutonic rock. Contains essential quartz, plagioclase and alkali feldspar, usually with hornblende and/or biotite and/or muscovite. Granodiorite: a plutonic rock with essential quartz and plagioclase, with lesser amounts of alkali feldspar and small amounts of hornblende and biotite.

Where can I find igneous rocks? ›

Igneous rocks occur in a wide range of geological settings: shields, platforms, orogens, basins, large igneous provinces, extended crust and oceanic crust.

Intrusive rocks are those that are formed when magma cools and solidifies within the Earth's crust. Examples of such rocks are Granite and Diorite. Extrusive rocks are those that are formed when magma cools and solidifies at the surface of the Earth's crust. Examples of such rock include Basalt and Pumice.

Igneous Rocks - Igneous rocks are formed by volcanoes. When a volcano erupts, it spews out hot molten rock called magma or lava. Eventually the magma will cool down and harden, either when it reaches the Earth's surface or somewhere within the crust. This hardened magma or lava is called igneous rock.

Igneous: Igneous rocks form from the cooling of melted rock (either lava or magma) into solid form. If the cooling occurs underground, the rock is an intrusive, or plutonic, igneous rock. If the cooling occurs on the earth's surface, the rock is an extrusive or volcanic rock.

These rocks include: andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff. Pictures and brief descriptions of some common igneous rock types are shown on this page.

Intrusive igneous rocks solidify within Earth. These rocks are also known as plutonic rocks—named for Pluto, the Roman god of the underworld. Intrusive igneous rocks are generally wholly crystalline and characterized by large crystal sizes visible to the naked eye because they cool slowly.

Selected rocks in these canyons include: (1) igneous rocks: quartz monzonite, (2) metamorphic rocks: quartzite, slate, gneiss, and marble, and (3) sedimentary rocks: shale, limestone, sandstone, siltstone, and conglomerate.

Basic rocks such as gabbro, dolerite and basalt are poor in silica and contain the minerals olivine, pyroxene, feldspar and/or quartz among others; they are also rich in the metals magnesium and iron and are often described as “mafic”. The intermediate rocks include diorite, microdiorite and andesite.