Minerals

I'll be having my report on Monday, I hope everyone will like it..

Fascinating Fact The largest topaz crystal was found in Brazil in 1940. It weighs 596 pounds. It is on display in the American Museum of Natural History in New York.

You are probably wondering how scientists have identified over 2,000 minerals. Well, minerals have certain properties, or characteristics, that help to identify them. Minerals can be identified by their color, luster, streak, cleavage, hardness, specific gravity, and even by their chemical composition. Below you will find a table of some of these properties. Also, included are some examples of minerals that help explain these properties. There are also links to webpages that have additional information about each of the properties described below. Hopefully, this information will help you to become a good mineral detective. GOOD LUCK! Color Color is not always a good clue to the identity of a mineral. Many minerals are found in several colors and many minerals have extra chemicals in them that give them an unexpected color. Also,weathering may change the color of the mineral. Example-quartz comes in various colors: rose, milky, clear To the TOP Luster Luster is the way a mineral reflects light. Minerals can be described as metallic, pearly, glassy, silky, greasy, brillant, or dull. For example, diamonds are brillant. Talc has a greasy luster, quartz has a glassy luster, and gypsum has a pearly luster. Pyrite or fool's gold, as it is sometimes called, has a metallic luster. To the TOP Streak This is the color of the streak made by rubbing a mineral across a hard, rough surface like a bathroom tile. An example is pyrite which is a brassy, yellow color. However, it makes a greenish, black streak when rubbed across a rough surface. You will need a field guide to rocks and minerals to tell you what color streak a mineral makes. To the TOP Cleavage Cleavage is when certain minerals break in a definite way. For example, galena cleaves into little cubes. Mica cleaves into thin sheets. Calcite cleaves into slanting bricks. Feldspar breaks into little steps. Quartz cleaves into irregular chunks. To the TOP Hardness Hardness is measured by seeing how easy it is to scratch a mineral. It is usually stated in terms of the Moh’s Scale. They are arranged from the softest to hardest. Talc        5. Apatite 9. Corundum Gypsum    6. Orthoclase Calcite     7. Quartz 10. Diamond Fluorite   8. Topaz For example, talc, the softest mineral known, can be scratched with a fingernail. Diamond, the hardest mineral, can scratch all the other minerals but cannot be scratched by them. A German mineralogist, Friedrich Mohs, developed a standard scale of hardness in 1822. His scale is so easy to use that it is still in use today.This was called the Moh’s Scale. To the TOP Specific Gravity Specific gravity of a mineral is its relative weight compared to the weight of an equal volume of water. It determines the density of the mineral. Two minerals may be the same size, but their weight may be very different. Water has a specific gravity of 1. If a mineral has a specific gravity less than 3, it is considered a "light" mineral, between 3 and 5 - "average", and more than 5 - "heavy". Minerals with a metallic luster are usually "heavy".