Rocks and Minerals

Rocks and Minerals

Rubies, Diamonds, Silver and Gold are some of the most beautiful and valuable products of the earth's crust. These treasures as well as more common substances such as quartz are all minerals.

Did you Know? Minerals are substances that are In Job 28: 1-2 it talks found naturally in the earth and have a about Rocks and Minerals? crystalline structure, their atoms are It says” Surely there is a in an orderly arrangement. They are vein for the silver, and a the building blocks of rocks and soil, place for gold where they and many are vital to industry and fine it. Iron is taken out of society. the earth, and brass is Minerals are either elements or molten out of the stone.’’ compounds. Only a few minerals are found in the earth's crust as elements. Most minerals are compounds.

Minerals may be classified into several groups based on their chemical composition. The smallest group consists of the native elements, substances that exist naturally in the earths crust as single, uncombined elements although they may also form compounds. The Fifty or so native elements include gold, sulfur, carbon ( such as diamond) copper and arsenic.

Another group known as the halides, consists of compounds made with the elements fluoride, chlorine, bromine, or iodine. These minerals include halite, sylvite, and fluorite. Only a handful of halides are common in the earth's crust. Here are some of their names. Sulfides and sulfates, oxides, carbonates, phosphates, silicates.

One characteristic shared by all minerals is that they form crystals, geometric structures that are composed of atoms of molecules and have an orderly arrangement. Some crystals may be several meters long, others may be so small that a powerful microscope is needed to see them.

Identifying Minerals

Identifying Minerals Some minerals can be identified by their geometric shape, but other physical characteristics can help differentiate between similarly shaped minerals. Its sometimes necessary to analyze the color, density, and the hardness of a mineral to determine its identity.

For some minerals, color is a defining property, in such cases, the color of the sample helps to identify the particular mineral. Similarly colored minerals can often be differentiated by scraping the crystal on a piece of unglazed porcelain called a streak plate. The mineral leaves a line of powder called a streak on the plate. The color of the streak, unaffected by tarnish or impurities, can be used to identify the mineral.

The way light is reflected from the surface of a mineral is called luster. Luster is independent of color, although testing minerals for color and luster both involve inspecting samples of minerals in light. The resistance of a smooth surface of a mineral to being scratched is called its hardness. The hardness test is done by scratching a mineral sample with an instrument of known hardness. If the sample is scratched, it is softer than the instrument, but if the sample is not scratched it is harder than the instrument.

The tendency of a mineral to break readily along certain flat surfaces, or planes, producing fragments with the same shape as the parent mineral, is called cleavage. Each mineral splits in a specific way.