Mineral Properties, Uses, and Identification Minerals An inorganic, naturally occurring solid that have a definite chemical composition, distinctive physical properties and a crystalline structure. These are the five things that define a mineral: • Inorganic • Naturally Occurring • Solid • Definite Crystalline Structure • Definite Chemical Composition How many minerals are there??? > 5300 known minerals! What is the difference between a mineral and a rock? Physical Properties • • • • • • Shape Luster Color Hardness Streak Cleavage • • • • • • Texture Magnetism Specific Gravity Taste Odor Effervesces with HCl Note: there are more than this that will be very important to your mineral identification skills should you choose to take a mineral class later. Shape: Crystal Habit Every mineral has a crystal form. The crystal form is the shape that a crystal will take if it grows unimpeded and unbroken Shape: Crystals vs. Granules • Important : Most mineral specimens are irregular grains, very few display their characteristic crystal habit. HowMineral many 1 minerals are 1 Crystal there? Mineral 2 Many Crystals Luster: Metallic vs. Non-Metallic • Luster: a reflective property of mineral surfaces. • Usually we begin by separating the Metallic and Non-Metallic minerals. • Minerals can be further divided into subcategories based on luster • Important: Some minerals exhibit both metallic and non-metallic properties. Luster: Metallic There are two types of metallic minerals: Metallic and Sub-Metallic. Luster: Non-Metallic • • • • • • • • Adamantine Resinous Glassy/Vitreous Pearly Greasy/Oily Silky Dull Earthy Color • Wavelengths of visible light are absorbed or reflected by the mineral • Some minerals change color or have various forms of different color • Sometimes color is determined by trace elements. • You cannot rely on color when it comes to mineral identification. Hardness Streak Color of a powdered mineral which is tested by rubbing the mineral across a porcelain streak plate. Breakage Cleavage: Tendency of a mineral to break along flat planes of weaker bonding. • Cleavage Planes 0+ Fracture: Cleavage is absent and mineral breaks irregularly Cleavage The ability of a mineral to break or come apart in a consistent way • Breakage is along atomic planes • Cleavage is consistent with crystal symmetry and may be one to multidirectional from one mineral to another. • Reported as planes Cleavage Cleavage Angles • Some Minerals have special cleavages • Amphiboles – Hornblende – 120⁰ and 60 ⁰ • Pyroxenes – Augite – 90⁰and 90⁰ Fracture Describes the inability of a mineral to break in a consistent way and therefore not along cleavage planes Conchoidal- a smooth, curved breakage in all directions Other Physical Properties Magnetism: Some minerals are magnetic. This ranges from weakly to strongly magnetic. Specific Gravity: The specific gravity of a material is a comparison of its weight with the weight of an equal volume of water. Specific gravity measures the density of a material. Taste: Some minerals exhibit a specific taste. (i.e. Halite and Sylvite) Odor: Some minerals have a specific smell. (i.e. sulfur) Effervesces with HCl: Fizz or give off bubbles. Mineral Uses Practice Sample # Hardness Luster 1 Color/ Streak Color: green 4 Nonmetallic Streak: green Cleavage/ Fracture Cleavage: Poor, 0 planes Fracture: Good Other Properties Mineral Name Slight fizzing Malachite Encrusting nature Bright, distinctive green