1. Minerals

2. A mineral is a. NATURAL INORGANI C CRYSTALLI NE CHEMICAL COMPOSITI ON

3. Chemical Composition of Minerals Ex: Sulfur = S Ex: Fluorite = CaF 2 (combinatio n of calcium and fluorine) RT = Pg. 16

4. Crystalline Structure of Minerals The atoms with a mineral are arranged and bonded in a specific way creating the crystalline structure of the mineral. The crystalline structure of a mineral helps to determine that mineral’s physical and chemical properties – such as hardness and cleavage. The majority of the Earth’s crust (by mass and volume) is made up of the elements oxygen and silicon. The “silicon-oxygen tetrahedron” is the basic building block of many minerals.

5. Rock vs. Mineral A rock is a All minerals are rocks, but not all rocks are minerals. Most rocks are composed of one or more minerals. Some rocks are composed of glassy or organic materials COAL OBSIDIAN

6. Mineral Properties and Identification The best method for mineral identification is through the use of X- ray diffraction. A beam of X-rays passing through a mineral sample will diffract leaving a unique “x-ray pattern” on photographic film. Each mineral has its own unique diffraction pattern. Minerals have a unique set of physical and chemical properties that reflect its internal arrangement of atoms. When in the field, scientist will use other methods to identify minerals.

7. Mineral Properties and Identification Color The color of a mineral can be used for identification in some cases. Many times minerals will change due to impurities found SULFUR Sulfur is well known for its yellow color. QUARTZ All three samples are of the same mineral. In this case color would not be useful tool in mineral identification.

8. Mineral Properties and Identification Streak The streak color does not always match the color of the mineral. The streak of a mineral is more consistent than the color of a mineral and, therefore, is a more reliable test for mineral identification. HEMATITE Hematite is a silver colored mineral. When scratched on a porcelain plate, its streak is reddish-brown.

9. Mineral Properties and Identification Luster A mineral with a metallic luster shines like a metallic surface (Ex: clean steel pot). Most minerals have a nonmetallic luster. PYRITE Pyrite has a metallic luster and shines like a metallic surface in the light. OLIVINE Olivine does not shine like a metallic surface in the light. It has a nonmetallic luster.

10. Mineral Properties and Identification Hardness Moh’s Hardness Scale is a tool used by scientists to determine the hardness of a mineral. Scientists can determine whether an unknown mineral can “scratch” or be “scratched” by known common materials. This will help a scientist determine the hardness of an unknown mineral. Gypsum has a hardness of 2 and calcite has a harness of 3. A fingernail has a hardness of 2.5. A fingernail can “scratch” gypsum and “be scratched” by calcite.

11. Mineral Properties and Identification Cleavage Zones of weakness found within a mineral relate to the crystalline structure of the mineral. Sometimes zones of weakness can be seen as smooth sides with a luster. MUSCOVITE MICA GALENA CLEAVAGE: Zones of weakness FRACTURE: Uneven brake

12. Mineral Properties and Identification Other Tools for Mineral Identification Specific Gravity Crystal Shape Reaction with HCl acid