Mineral Properties How do we know what stuff is?

Each mineral has it’s own properties Minerals are different in some way from one another Minerals are different in some way from one another How can we tell if one mineral is another? How can we tell if one mineral is another? –By it’s physical properties

Look at the pretty colors Minerals usually aren’t determined entirely by color Minerals usually aren’t determined entirely by color –Some of the same minerals may have different colors A few minerals have very distinctive colors that can help them be identified A few minerals have very distinctive colors that can help them be identified Color can be used to narrow a search or to eliminate a possible choice Color can be used to narrow a search or to eliminate a possible choice

Were going Streaking While color of minerals isn’t terribly consistent from sample to sample streak is much more accurate While color of minerals isn’t terribly consistent from sample to sample streak is much more accurate –Streak is simply the mineral in powder form Darker metallic minerals usually leave dark streaks Darker metallic minerals usually leave dark streaks Non-metallic usually don’t leave much if any of a streak Non-metallic usually don’t leave much if any of a streak

Luster Luster is how light is reflected off of the surface of the mineral Luster is how light is reflected off of the surface of the mineral –If the surface appears to look like metal it’s called a metallic luster  Regardless of color –If they are non-metallic they go by many other names  Glassy, pearly, silky, earthy, etc.

Crystalline structure Each mineral has it’s own crystal structure Each mineral has it’s own crystal structure –If the mineral is allowed to form in enough space the structure will be obvious –If the mineral is not allowed to form in enough space it will be more random and difficult to see crystal structure

Hardness One of the most useful properties of a mineral is it’s hardness One of the most useful properties of a mineral is it’s hardness –Hardness is the resistance to being scratched The scale they use is called the Moh’s scale of hardness The scale they use is called the Moh’s scale of hardness –It is a list of 10 minerals ranked 1-10  1 being softest 10 being hardest Talc =1 while diamonds = 10 Talc =1 while diamonds = 10

More Hardness If Mineral A is harder then Mineral B If Mineral A is harder then Mineral B –A will be unharmed while B will have a mark on it Exact values can’t be calculated by this scale Exact values can’t be calculated by this scale –They must be in ranges  It must be a range between a mineral it’s harder then and one it’s softer then

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Hardness again! Some Common objects used to determine hardness Some Common objects used to determine hardness –Fingernail (2.5), Penny (3.5), Nail(4.5), Glass (5.5), Streak plate(6.5) –A piece of true glass is harder then a nail  This means that glass will not be scratched by a nail, that has nothing to do with breaking

Cleavage Cleavage is the tendency for an object to break, or separate into smooth surfaces Cleavage is the tendency for an object to break, or separate into smooth surfaces –Some may have one, or many This will give us the best idea of the molecular structure This will give us the best idea of the molecular structure –Where the chemical bonds are the weakest they will break –This causes the surface to be very smooth

Fracture and not your arm Fracture is the term used to describe the way a mineral breaks without any distinct cleavage Fracture is the term used to describe the way a mineral breaks without any distinct cleavage –If a mineral has 0 cleavage planes it is said to fracture Fracturing occurs because the minerals chemical structure is strong on all sides Fracturing occurs because the minerals chemical structure is strong on all sides

Density Density is the amount of matter in a given space Density is the amount of matter in a given space The formula for density is The formula for density is D = m / v D = density m = mass v = volume