Minerals 2/11/14

Rocks and Minerals A rock is a solid combination of minerals or mineral materials A mineral is a naturally occurring, inorganic solid with a crystal structure and a characteristic chemical composition Today, we are going to focus on minerals…

Minerals Minerals are inorganic, which means that living things did not produce them Is coal a mineral? Is concrete a mineral? No, coal is created from the remains of plants No, concrete is human manufactured and made from a variety of natural materials

Minerals Each mineral is a unique substance with its own chemical composition and crystal structure Within each mineral, the chemical composition is nearly constant Pyrite is made of iron and sulfur (FeS2)

Minerals Minerals are the building blocks of rocks Over 4,000 minerals exist Only a fraction are common Common minerals are call rock forming minerals

Properties of Minerals Crystal Structure Atoms are arranged in a particular geometric shape Size of mineral’s crystal structure can vary for the same type of mineral Examples of structure include: Cubes, sheets, needles, and threads Pyrite has a cubic crystal structure 

Properties of Minerals Color SOME minerals can be identified by a characteristic color Color can be deceptive due to slight changes in composition

Properties of Minerals Streak Streak is the color of the mineral’s powder on a streak plate It is found by scraping the mineral across a piece of unglazed porcelain (streak plate) The color of the streak is not always the same color as the mineral itself

Properties of Minerals Luster Luster is the way in which its surface reflects light Refers to general appearance of a mineral (how shiny it is) Terms used to describe luster include: Silky, pearly, vitreous (glassy), earthy, metallic, greasy Pearly Earthy Vitreous

Properties of Minerals Density Density depends on chemical composition Density describes how “Tightly Packed” the atoms and molecules are. (Density = mass/volume) The densest elements are the METALS in the Middle of the Periodic Table The least dense elements are at the ENDS of the periodic table (group 1 and 8) Galena is made mostly of lead so its density is about 7.5 g/cm3

LESS. Oxygen is naturally a gas, and silicon is a metalloid LESS! Oxygen is naturally a gas, and silicon is a metalloid. Lead is a dense element in the middle of the transition METALS. Does Quartz, which is made of Silicon (Si) and Oxygen (O), have a higher or lower density than Galena (Pb)?

Properties of Minerals Hardness Atoms in different minerals are held together by chemical bonds of different strengths, resulting in a different hardness Hardness is the resistance to scratching “Moh’s Hardness Scale”

Check for Understanding Which mineral can scratch Gypsum but cannot scratch Fluorite? What are three different ways to classify a mineral’s luster? What is Streak? Calcite! Glassy, greasy, metallic Color of the mineral’s powder

Properties of Minerals Fracture and Cleavage Fracture of a mineral is how the mineral breaks Uneven or curved (chonchoidal) Cleavage is a type of fracture in which the mineral tends to split along regular, well-defined planes where the bonds are the weakest Blocks, sheets, etc.

Properties of Minerals Other Properties Acids Magnetite Fluorescence Electrical Refraction