Minerals Properties…..

What is a Mineral?  A mineral is :  crystal structure  definite chemical composition.  Must occur naturally  Must be inorganic  (Can’t be from anything once alive)  Always a solid  A mineral is :  crystal structure  definite chemical composition.  Must occur naturally  Must be inorganic  (Can’t be from anything once alive)  Always a solid

Identifying Minerals: Specific Properties  Each mineral has its own specific properties that can be used to identify it.  Some are observable with the naked eye- some need to be tested  Properties include: Hardness, Color, Streak, Luster, Density, Crystal Shape, Cleavage and Fracture, etc  Each mineral has its own specific properties that can be used to identify it.  Some are observable with the naked eye- some need to be tested  Properties include: Hardness, Color, Streak, Luster, Density, Crystal Shape, Cleavage and Fracture, etc

Color  Observable on the surface  Easy to identify, but not reliable  Physical property  Only useful for a few minerals that have characteristic color  Examples: malachite=green; azurite=blue  Observable on the surface  Easy to identify, but not reliable  Physical property  Only useful for a few minerals that have characteristic color  Examples: malachite=green; azurite=blue

Streak  The color of the powder left by a mineral if it is rubbed against an unglazed tile called a streak plate  Streak color is always the same; CHARACTERISTIC Property  Useful property for identification of softer materials  Harder minerals do not have a streak  Streak color and mineral color is often different  Ex: pyrite mineral=gold color and streak=greenish black  The color of the powder left by a mineral if it is rubbed against an unglazed tile called a streak plate  Streak color is always the same; CHARACTERISTIC Property  Useful property for identification of softer materials  Harder minerals do not have a streak  Streak color and mineral color is often different  Ex: pyrite mineral=gold color and streak=greenish black

Hardness  The ability of a mineral to resist being scratched  One of the most useful properties  Moh’s Hardness Scale  Developed by Frederick Mohs  A scale for hardness: ranks ten minerals from softest to hardest; if scratched by the known mineral, it is softer than it; if scratches the known material, it is harder than it  The ability of a mineral to resist being scratched  One of the most useful properties  Moh’s Hardness Scale  Developed by Frederick Mohs  A scale for hardness: ranks ten minerals from softest to hardest; if scratched by the known mineral, it is softer than it; if scratches the known material, it is harder than it

Field Hardness Scale  Using tools to determine the harndess of minerals is actually using the “Field Hardness Scale”  Uses tools such as fingernail, knife, copper penny, glass, steel file  Used when all of the minerals from Moh’s are not available  How we will determine hardness in class.  Using tools to determine the harndess of minerals is actually using the “Field Hardness Scale”  Uses tools such as fingernail, knife, copper penny, glass, steel file  Used when all of the minerals from Moh’s are not available  How we will determine hardness in class.

Luster  The way mineral reflects light from its surface  Metallic- highly polished  Many of the minerals look “shiny” if you are saying that it is metallic- it means that it contains a metal- use the concept of ‘heft’ to eliminate false metallic observations  Nonmetallic- dull, glassy, silky  Other descriptors:  Earthy, waxy, pearly  The way mineral reflects light from its surface  Metallic- highly polished  Many of the minerals look “shiny” if you are saying that it is metallic- it means that it contains a metal- use the concept of ‘heft’ to eliminate false metallic observations  Nonmetallic- dull, glassy, silky  Other descriptors:  Earthy, waxy, pearly

Density  Amount of matter in a given space: Mass/ Unit Volume (g/cm 3 )  Characteristic to each mineral  Mineral is measured for mass using a triple beam balance and for volume using water displacement  Amount of matter in a given space: Mass/ Unit Volume (g/cm 3 )  Characteristic to each mineral  Mineral is measured for mass using a triple beam balance and for volume using water displacement

Cleavage and Fracture  The way a mineral breaks  Cleavage-smooth, definite break  Depends on how the atoms in its crystals are arranged  Fracture-uneven break  A variety of terms are used to describe this  Shell-shaped-curved, shell-like, like chipped glass  Hackly fracture-jagged points  Earthy fracture-crumble  Uneven fracture-rough, irregular surfaces  The way a mineral breaks  Cleavage-smooth, definite break  Depends on how the atoms in its crystals are arranged  Fracture-uneven break  A variety of terms are used to describe this  Shell-shaped-curved, shell-like, like chipped glass  Hackly fracture-jagged points  Earthy fracture-crumble  Uneven fracture-rough, irregular surfaces

Crystal Shape  Cubic  Hexagonal  Tetragonal  Orthorhombic  Triclinic  Cubic  Hexagonal  Tetragonal  Orthorhombic  Triclinic

Special Properties  Fluorescence-glows when under ultraviolet light  Magnetism-naturally magnetic  Electrical-pressure applied produces a small electrical current  Reaction to acid  Radioactive  Double Refraction- Calcite/Halite  Fluorescence-glows when under ultraviolet light  Magnetism-naturally magnetic  Electrical-pressure applied produces a small electrical current  Reaction to acid  Radioactive  Double Refraction- Calcite/Halite