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