Transcript Minerals
Minerals A mineral is a. NATURAL INORGANI C CRYSTALLI NE CHEMICAL COMPOSITI ON Chemical Composition of Minerals Ex: Sulfur = S RT = Pg. 16 Ex: Fluorite = CaF2 (combinatio n of calcium and fluorine) 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. 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 Mineral Properties and Identification The best method for mineral identification is through the use of Xray 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. Mineral Properties and Identification SULFUR Sulfur is well known for its yellow color. Color QUARTZ All three samples are of the same mineral. In this case color would not be useful tool in mineral identification. The color of a mineral can be used for identification in some cases. Many times minerals will change due to impurities found Mineral Properties and Identification Streak The streak color does not always match the color of the mineral. HEMATITE Hematite is a silver colored mineral. When scratched on a porcelain plate, its streak is reddish-brown. The streak of a mineral is more consistent than the color of a mineral and, therefore, is a more reliable test for mineral identification. Mineral Properties and Identification PYRITE Pyrite has a metallic luster and shines like a metallic surface in the light. Luster OLIVINE Olivine does not shine like a metallic surface in the light. It has a nonmetallic luster. A mineral with a metallic luster shines like a metallic surface (Ex: clean steel pot). Most minerals have a nonmetallic luster. Mineral Properties and Identification Hardness 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. 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. Mineral Properties and Identification MUSCOVITE MICA CLEAVAGE: Zones of weakness GALENA FRACTURE: Uneven brake 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. Mineral Properties and Identification Specific Gravity Crystal Shape Reaction with HCl acid Other Tools for Mineral Identification