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Earth’s Buried TreasuresAn Introduction to Mineral Identification
Earth Science
How is the shape of a mineral related to it’s internal structure?
• The crystalline structure and properties of a mineral depends upon the internal arrangement of the mineral’s atoms.
The Properties of Minerals
The first thing we notice about a mineral is usually its outward appearance. This outward appearance is a result of the internal arrangement of atoms.
Graphite and diamond are both elemental carbon but have different properties because of their internal arrangement of atoms.
Mineral Properties
Luster is the appearance of light reflected from the surface of the mineral
• Metallic• Non Metallic
– Earthy– Vitreous– Pearly – Silky– Resinous
Color is the least reliable of all physical properties
Different colors are due to impurities or the presence of metals in the magma from which the mineral formed
Mineral Properties
Mineral Properties
Hardness is the minerals ability to resist scratching
Mineral PropertiesStreak is the color of the mineral in it’s powdered form
– Obtained by scratching on a Streak Plate
Cleavage is a property that is demonstrated as minerals break along weak planes of bonding– Easier understood as “if you break the
mineral it will always “cleave” in the same shape
– Cleavage is measured by number of cleavages and angle. Cleavage angle is determined by a contact goniometer.
Mineral Properties
When a mineral does not demonstrate cleavage it is said to Fracture– Conchoidal and Fibrous are 2 examples
The mineral Quartz demonstrates fracturing whereas the calcite on the left demonstrates cleavage
Mineral Properties
Specific Gravity compares the density of the mineral to the density of an equal amount of water
– So….No Units
Crystal Form (and most mineral properties) is the external expression of the mineral’s internal arrangement of atoms
Mineral Properties
Other properties that may be used to identify a mineral are:
• Smell • Malleability• Magnetism •Double refraction•Taste•Density
Mineral Properties
• Placing a drop of Hydrochloric acid onto a mineral that is composed of a “carbonate” demonstrates the property known as an Effervescent Fizz
Fluorescent minerals are certain minerals that when exposed to ultraviolet radiation (light) they emit visible light. Another way to describe this process of fluorescence is when invisible short wavelength radiation is absorbed by a material and then is converted and remitted as a longer wavelength.
Earth’s Buried TreasuresAn Introduction to Mineral Identification
Conclusion