Minerals in Kansas
Minerals are solids formed from naturally occurring processes. Most minerals are inorganic solids. Inorganic means nothing in the mineral was derived directly from plants, animals, or other organisms. Typical animal structures are made up of cells, but some shells and skeletons are composed of minerals instead. Most minerals form underground through processes involving water, evaporation, cooling, heat, or pressure.
Minerals are made of smaller units called elements. A few minerals, called native elements, are made of only one type of element. Of the 20 native elements, sulfur is the only one that occurs naturally in Kansas, and it is found only in small quantities. All other minerals in the state are chemical compounds—a combination of two or more elements.
Chemical compounds are formed when two or more elements are chemically bonded together. For example, the chemical compound calcium carbonate is a combination of the elements calcium (Ca), carbon (C), and oxygen (O).
Chemical formulas are symbolic expressions of chemical compounds. The chemical formula for calcium carbonate is CaCO3. The formula tells us that the ratio of calcium to carbon to oxygen is 1 (Ca) to 1 (C) to 3 (O3). The "3" after the "O" means that for every atom of calcium and carbon in the bond, there are three atoms of oxygen.
Because the mineral calcite is a calcium carbonate, its chemical formula is CaCO3. No matter where calcite is found on Earth, it will have the chemical formula CaCO3. Two minerals may have the same chemical formula but are different minerals because they have different crystal structures. Calcite and aragonite, for example, are both calcium carbonates (CaCO3).
Minerals are crystals, meaning their atoms are arranged in regular, ordered, and repeated patterns. When crystals have had enough time and space to grow large, you can see them without the aid of a magnifying glass or microscope. In nature, however, crystals are often microscopic because they are competing for space with adjacent atoms and have very little room to grow.
Rocks are mainly made up of minerals. A rock may be composed of just one type of mineral, but most are a mix of minerals. A layer of sandstone, for instance, may contain particles of the minerals quartz, calcite, and silica compacted together.
Physical Properties of Minerals
Minerals can be identified by physical properties, including
Color is consistent in a few minerals, such as gold, which is always yellow. Other minerals come in many different colors due to small variations in chemistry. Quartz, for example, can be clear, white, pink, purple, yellow, or smoky brown.
Luster is how a mineral looks in reflected light. Some minerals are shiny while others are dull. Common mineral lusters are metallic, glassy, silky, pearly, and chalky.
Cleavage is the tendency of some minerals to break along flat surfaces. Mica breaks apart in thin sheets. Calcite breaks in a rhombic shape (like a distorted, or squashed, cube). Halite breaks into cubes. Not all minerals have strong cleavage.
Hardness is determined by the resistance of a mineral to scratching. The Moh’s Scale of Hardness (named after the man who established it) lists minerals from 1 (softest) to 10 (hardest). A mineral of a higher hardness will scratch a softer mineral. You can test a mineral’s hardness on everyday items such as a fingernail (hardness = 2.5), a copper penny (hardness = 3), and a glass plate or steel knife (hardness = 5.5). Calcite, which has a hardness of 3, will scratch your fingernail but not a glass plate. Quartz, with a hardness of 7, will scratch both. The following minerals range in hardness from 1 to 10:
Streak is the mark some minerals leave on an unglazed porcelain plate. Minerals with a hardness of less than about 7 will leave a streak on the plate. The color of a streak, which can be a different color than the mineral, helps identify the mineral. Galena, which is lead gray, leaves a lead gray to black streak. Hematite, an iron ore mineral that may be black or gray, leaves a reddish brown streak.
Specific gravity is a measure of the density of a mineral. You can make a rough comparison of the specific gravity of two minerals by testing how heavy a piece of one of the minerals feels compared to a similarly sized piece of the other. For example, if you held a piece of quartz (specific gravity of 5.26) in one hand and a piece of hematite (specific gravity of 2.65) in the other hand, the quartz would feel about twice as heavy as the hematite.
Amount of transparency depends on how much light can pass through a mineral. If light can pass through and you can see through the mineral to objects on the other side, the mineral is transparent. If light can pass through but you can’t see through it, the mineral is translucent. If light can’t pass through, the mineral is opaque.
Buchanan, R., 2010, Kansas Geology: An Introduction to Landscapes, Rocks, Minerals, and Fossils (2nd ed.): Lawrence, Kansas, University Press of Kansas, 240 p.
Buchanan, R., and McCauley, J. R., 2010, Roadside Kansas: A Traveler's Guide to Its Geology and Landmarks (2nd ed.): Lawrence, Kansas, University Press of Kansas, 392 p.
Kansas Rocks and Minerals, Kansas Geological Survey Educational Series 2
Kansas Geological Survey, 2001, Industrial Minerals in Kansas.