earth sci.pdf

EARTH SCIENCE QUARTER 1: LESSON 3: ROCK-FORMING MINERALS Minerals themselves are made up of one or a number of chemical elements with a definite chemical composition. Minerals cannot be broken down into smaller units with different ch...

EARTH SCIENCE QUARTER 1: LESSON 3: ROCK-FORMING MINERALS Minerals themselves are made up of one or a number of chemical elements with a definite chemical composition. Minerals cannot be broken down into smaller units with different chemical compositions in the way that rocks can. Physical Properties of Mineral There are several different mineral properties which must be identified and defined. 1. Luster- refers to how light is reflected from the surface of a mineral. 2. Hardness – it is the ability of mineral to resist scratching. Friedrich Mohs, a German mineralogist, developed a hardness scale over 100 years ago. The hardest mineral known, diamond, was assigned the number 10. It is called the Mohs Hardness Scale. It ranks the order of hardness of minerals and some common objects. The Mohs Scale of Hardness measures the scratch resistance of various minerals from a scale of 1 to 10, based on the ability of a harder material/mineral to scratch a softer one. 3. Crystal Form Habit – refers to the characteristic shape of a mineral unit which are visible (either an individual crystal or a group of crystal). 4. Color – one of the most obvious characteristics of a mineral, but generally not the most useful diagnostic feature. Minerals are colored because certain wavelengths are absorbed and the color results from the combination of those wave lengths that reach the eye. 5. Streak – is the mineral’s color in powdered form. It can be useful for identifying metallic and earthy minerals. Non-metallic minerals usually give a white streak because are very light- colored. Other minerals may have very distinctive streaks. Hematite- for example, always gives a reddish-brown streak no matter what type of luster it displays. 6. Cleavage – it is the ability of a mineral to break along preferred planes. The number of cleavage planes in a mineral may also aid its identification. Cleavage typically occurs in either one, two, three, four or six dimensions. The tendency of a Mineral to break evenly along its weakest plane. 7. Fracture - Mineral breaks unevenly or irregularly.  8. Specific Gravity – is the “heaviness” of a mineral. It is defined as number that expresses the ratio between the weight of a mineral and the weight of a mineral and the weight of an equal volume of water. Water has a specific gravity of “1”. 9. Others – magnetism, odor, taste, tenacity, reaction to acid, etc. For example, magnetite is strongly magnetic; sulfur has distinctive smell; halite is salty; calcite fizzes with acid as with dolomite but in powdered form; etc. Chemical Properties of Mineral Mixtures are groups of molecules that can be separated by physical means. Compounds are groups of molecules with a definitive arrangement and can only be separated by chemical means. Minerals can be classified according to their chemistry, that is, their chemical composition. These classes are: Some of the Common Rock-Forming Minerals Along with their Physical and Chemical Properties Reference: SLM from Division of La Union (Author: GERLIE C. GUBATAN, MT-I)