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.
Dolomite is both a mineral and a rock. Dolomite is a calcium-magnesium carbonate. It is very similar to calcite and limestone in its chemical make up. Dolomite is white or light pink in color. It has a hardness of 3.5 - 4 and only will react to acid when it is heated or in powdered form. Dolomite is used as a building stone and as a source of magnesium.
Graphite and diamond are both pure carbon. The difference is the amount of heat and pressure that has been put onto the two minerals. Diamond is the hardest natural element on Earth with a hardness of 10 which is the maximum on the Mohs hardness scale. Graphite is a very soft mineral with a hardness between 1 and 2. Graphite has a black streak and was probably formed by the metamorphism of plant remains or by the crystallization of ancient magmas.
Today graphite is used for "lead" in pencils. Lead is poisonous to humans and has not been used for many years in pencils. Graphite is also used in the paint industry.
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 2500 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.
Hematite is mined in the Lake Superior and Appalachian mountain regions of the United States. Small deposits are found in many states of the union. Canada and Russia are leading countries in the mining of iron ore.
Kaolinite is a clay mineral which is formed by the weathering of feldspar. It is one of the most common minerals on Earth. Kaolinite can be found in all parts of the Earth. It is very soft with a hardness of 2-2.5. It has a color of white, pink or grey and a streak of white. The chemical make up is Al2 Si2 O5 (OH)4.
Kaolinite is used in the ceramics industry for the production of clay products.
Pyrite is also known as iron sulfide. It is one of the most common minerals on the Earth's surface. Many people call pyrite "Fools Gold" because the crystal resemble gold in color. Pyrite is much harder than gold and it looses its glitter quickly when exposed to the air. In fact when it is rubbed on a streak plate the streak will be green to dark gray. Pyrite has a hardness of 6.5 on the Mohs hardness scale. Its cleavage is cubic or not distinct.
Quartz is a common mineral that is found in many different types of rocks. The chemical formula is Silicon oxide (SiO2). One type of quartz is easily identified by its hexagonal crystals, but quartz can also be found in a large mass. Quartz can be broken or weathered into the tiny pieces we know as sand. Quartz is a very hard mineral and in fact is the hardest of the common minerals. Quartz is number seven on the Mohs hardness scale. Quartz is also chemically stable, which means that it weathers very slowly.
Quartz can be colored yellow, milky white, rose, smoky (brown or black), and the best known of the colored crystals amethyst, which is purple. Impurities in the rock at the time of formation causes the quartz crystal to have these different colors.
Quartz is used by humans in producing optical instruments and electrical devices. It is also used to make sandpaper and grinding tools.