BBC Bitesize - KS3 Chemistry - Rocks - Revision 2
Basalt is clearly the most common volcanic rock on Earth and basaltic rocks ( including gabbro, diabase and their metamorphosed equivalents) are the most. Gabbro. A plutonic basalt. Pictures of Igneous Rock Types. State of New these in the field and calls them granitoids pending laboratory tests. .. See its relation to the other plutonic rocks in the QAP classification diagram. Island gabbro; 8, Chapel island basalt; 9, Toms Brook gabbro. Map is modified after an intrusive relationship with the surrounding sedimentary rocks, but no.
Fracture occurs when a mineral breaks at random lines instead of at consistent cleavage planes. Many minerals that have no cleavage or poor cleavage fracture easily. The on the far right is a good example of a rock that has conchodial glass like fracture.
Quartz is a mineral that also has conchodial fracture. Only two minerals on earth are magnetic. They both have high quantities of iron. Magnetite is one of the magnetic minerals and pyrrhotite is the other. Magnetite was used by ancient sailors for compasses.
They would chip off needles of magnetite and float them on water and watch the needle point to the north. The photo above shows small pieces of metal fillings magnetically attached to magnetite! The rock is a natural magnet! Calcite is pure calcium carbonate CaCO3. It is found in limestone and marble. It is the cementing agent that binds sediments together into sedimentary rocks. Marble is metamorphosed changed by heat and pressure limestone. The crystals formed from pure calcite are in the form of a perfect rhomboid.
A rhomboid is a six-sided solid object in which the opposite sides are parallel. It has perfect cleavage in three directions. If you hit calcite with a hammer it will break into smaller but perfectly shaped rhomboids. Calcite is number two on Mohs hardness scale. Calcite is the material that forms stalactites and stalagmites in caves. Calcite is used as a fertilizer, cement, chalk, building stone, and for the manufacture of optical instruments.
Talc is a mineral that has perfect cleavage and a greasy or soapy feel. It is given the distinction of being number 1 on Mohs hardness scale.
Talc is also called soapstone which is used by artists for sculptures. Talc can be ground up into talcum powder. Ground talc is also used to make crayons, paint, paper, and soap. Talc is quarried in many Northeastern states of the United States. Hematite is the most important source of iron ore in the world. The production of iron has been important to nations of the world for over years.
Today the addition of other minerals to iron has lead to the production of steel which is vital to the economy of the major countries on Earth. Hematite has a red or black color but the streak is always red. The iron in the hematite turns red when it comes in contact with water and oxygen. In other words this rock is rusted!! Hematite has a metallic or earthy luster. The hardness of hematite is about 5 on Mohs hardness scale.
It has no cleavage and breaks with an uneven fracture. The reddish landscape of Mars is due to the oxidized iron on its surface. This tells us that water and oxygen must have been present on Mars at one time. Small deposits are found in many states of the union.
Canada and Russia are leading countries in the mining of iron ore.
Magnetite is a mineral that has a very high iron content. Magnetite has a black or brownish-red color and a black streak. It has a hardness of about 6 on the Mohs hardness scale. It is one of two minerals in the world that is naturally magnetic. Magnetite, also known as lodestone, is found throughout the United States. Magnetite is an important source of iron ore and occurs in many igneous rocks.
Chapter 4 Rocks and Minerals
There is a city in Russia by the name of Magnitogorsk that received its name because of the unusually high quantities and quality of magnetite found in the mountains surrounding the city. Magnitogorsk is a leading iron manufacturing center in Russia today. Galena is an important source of lead.
Galena's chemical symbol is PbS, which is lead and sulfur. Galena may also contain silver. The United States is the leading producer of lead in the world. Lead was used in pencils and paint until it was found to be poisonous to humans.
Today pencil "lead" is made of another mineral called graphite.
Lead is used for fishing weights. Gabbro is a coarse-grained, dark-colored, intrusive igneous rock. It is usually black or dark green in color and composed mainly of the minerals plagioclase and augite. It is the most abundant rock in the deep oceanic crust. Gabbro has a variety of uses in the construction industry. It is used for everything from crushed stone base materials at construction sites to polished stone counter tops and floor tiles. Igneous rock composition chart: A chart that illustrates the generalized mineral composition of igneous rocks.
By studying this chart, you can see that gabbros and basalts are composed mainly of plagioclase feldspar, micas, amphiboles, and olivine. What Minerals are in Gabbro? Gabbro is composed mainly of calcium-rich plagioclase feldspar usually labradorite or bytownite and clinopyroxene augite.
Basalt - Igneous rocks
Minor amounts of olivine and orthopyroxene might also be present in the rock. See composition chart on this page.
This mineral composition usually gives gabbro a black to very dark green color. A minor amount of light-colored mineral grains may also be present. Unlike many other igneous rocks, gabbro usually contains very little quartz. You can see a close-up view of gabbro toward the bottom of this page.
Gabbro and Basalt are Related Gabbros are equivalent in composition to basalts. The difference between the two rock types is their grain size. Basalts are extrusive igneous rocks that cool quickly and have fine-grained crystals.
Soil Genesis and Development, Lesson 1 - Rocks, Minerals, and Soils
Gabbros are intrusive igneous rocks that cool slowly and have coarse-grained crystals. In the oceanic crust, basalt forms near the surface at a divergent boundary, but gabbro forms at depth from slow crystallization. Learn about teaching plate tectonics. Gabbro in Oceanic Crust It is often stated that Earth's oceanic crust is made up of basalt.