From The Town Of Bedrock, Its a Place Right Out Of History

A MINERAL DEFINED  the solid portion of the earth is composed of rocks  rocks are composed of minerals  All minerals are defined by the following:  Naturally occurring: mother nature makes minerals…not us!  Inorganic: made of things that are not living and never will be living!  Solid: hard and breakable  Homogeneous: the same throughout  Definite chemical composition: unique combination of elements  Crystalline structure: repeating pattern of atoms that creates crystals

A MINERAL IDENTIFIED  There are 6 traits you can test to help you correctly identify a mineral sample 1. Color 2. Hardness 3. Streak 4. Cleavage/Fracture 5. Luster 6. Unique characteristics

COLOR  Color is okay to look at initially, but you can not base your decision only on that one trait  Why? Trace elements can vary the external color.  If we only looked at color, we would not identify it correctly. These are both diamonds

CAN YOU SCRATCH IT?  When you try to scratch a mineral, you are testing its hardness  If it can be scratched, then it is softer than the object you used to scratch it  If it cannot be scratched, then it is harder than the object you used to scratch it  Common minerals and their hardness are ranked on Moh’s Hardness Scale, listed from the softest to the hardest

FIELD HARDNESS CHART page 106

WE HAVE A STREAKER!!  The streak of a mineral is the mineral in its powdered form  Minerals will only have a streak if they are softer than the streak plate (which has a hardness of 7)  If the mineral has a metal in its chemical formula, it will usually leave a streak  The streak color will not always be the same color as the mineral…so don’t assume!

I NEED A BREAK!!!  Cleavage and fracture are two terms used to describe how a mineral breaks  Cleavage means it breaks with smooth, flat surfaces  Fracture means the mineral breaks along jagged surfaces

OH, HOW IT SHINES!  How a mineral shines describes its luster  If it shines like a metal, it has metallic luster  If it does not shine like a metal, it has nonmetallic luster 1. Dull 2. Glassy 3. Earthy 4. Pearly 5. Waxy

UNIQUE CHARACTERISTICS  Magnetism (magnetite)  Double refraction, double image (calcite)  Fizzes when acid is placed on it (calcite)  Fluorescence (glows under a black light)  Olfactory (sulfur) smell  Specific gravity: one of the best tests to help you identify a mineral !