Chapter 3 Minerals Updated November 2011

What is a Mineral? Mineral- a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition

Mineral – Naturally Occurring Must occur in the natural world Which of the following is naturally occurring? Plastic Brick Glass Quartz

Mineral - Inorganic The mineral cannot form from materials that were once part of a living thing. (Living things are said to be organic) Is coal a mineral? How does coal form?

How Coal Formed

Mineral – Crystal Structure Crystal structure - the repeating pattern of a mineral’s particles forms a solid. A crystal has flat sides (faces) that meet at sharp edges and corners.

Question # 7on the study guide This will not be on the test What does it mean when a mineral always contains certain elements in definite proportions?? It means that the mineral has a definite chemical composition. What?? Next slide:

Are almost all minerals compounds?? Yes! This means that they are made up of more than one chemical. Some are pure though: Question # 9: Name three pure crystalline elements: Gold Silver Copper

Mineral Identification There are 8 properties used to identify minerals. They are: Color Streak Luster Density Hardness Crystal Systems Cleavage and Fracture Special Properties

Mineral ID… Color – look at the mineral!!

Mineral ID… Streak – the streak is the color of its powder. To obtain this, rub the mineral against an unglazed porcelain tile. (The color of the streak is sometimes different than the mineral)

Mineral ID… Luster – describes how light is reflected from a mineral’s surface

There are 6 lusters of minerals Metallic Glassy (waxy, greasy, pearly) Submetallic Dull Silky Earthy

Mineral ID… Hardness – use Moh’s Hardness Scale Page 71 in the textbook Find hardness through a scratch test

Moh’s hardness scale cont.… Hardness can be determined by a scratch test. A mineral can scratch any mineral softer than itself. (But not any mineral harder) Example: To determine the hardness of azurite, you could try to scratch it with talc, gypsum, or calcite. But you discover none of them scratch it. Apatite, rated 5 on the scale does, therefore azurite’s hardness is about 4.

Mineral ID… Crystal Systems – 6 systems found on page 73 of the textbook They are: Cubic Hexagonal Ortrhorhombic Monoclinic Tetragonal Triclinic

Mineral ID… Cleavage and Fracture is the way a mineral breaks apart. Cleavage = a mineral that splits easily along flat surfaces

Fracture - how a mineral looks when it breaks apart in an irregular way

Mineral ID… Special Properties Fluorescence- Glows in UV light Magnetism- Attracts ferromagnetic materials Acid Test- reacts chemically Optical Properties- bends light Radioactivity- produces its own energy Electrical properties- conducts electricity