Minerals: Physical Properties. EARTH/SPACE SYSTEMS EARTH MATERIALS AND PROCESSES UNIT MINERALS SUB-UNIT. Mineral Characteristics. 1. A mineral occurs naturally. 2. A mineral is solid. 3. A mineral has a definite chemical composition.
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Minerals: Physical Properties
EARTH MATERIALS AND PROCESSES UNIT
Of the almost 4000 known minerals, only about 30 are common.
The most common are quartz,feldspar,mica, and calcite.
These minerals make up most of the rocks found in the Earth’s crust.
- Gold, Pyrite, and Chalcopyrite all have gold color, so you need additional information to identify these minerals
Streak of a mineral is the color of its powder when rubbed on an unglazed white tile.
The streak is often not the same color as the mineral.
A minerals color may vary, but the streak rarely will!
Luster refers to the way a mineral shines in reflected light.
Notice the difference between these two minerals?
The mineral on the left has a metallic luster, the one on the right, a nonmetallic luster.
There are several terms used to describe nonmetallic luster. Examples could be vitreous, like the quartz on the left, or pearly, like the gypsum on the right.
Other terms that might be used include greasy, dull, and earthy.
Can you tell which of these has an earthy luster and which has a vitreous luster?
- How did your group classify mineral 1?
- How did your group classify mineral 2?
- How did your group classify mineral 3?
- How did your group classify mineral 4?
- How did your group classify mineral 5?
Now your turn! A sample of Calcite has a mass of 324 grams and a volume of 120 ml (cm3).
What is its density?
320 grams / 120 cm3 = 2.7 g/ cm3
Quartz, Diamond, or Talc
Crystal shape can be a useful property to identify minerals if the minerals have had the time and space to form crystals. Most mineral grains that are found in rocks, lack the room to grow.
- Crystals of each mineral grow atom by atom to form that mineral’s crystal structure
- Geologists classify minerals into six groups based on the number and angle of the crystal faces.
The cleavage of a mineral is its tendency to split easily or to separate along flat surfaces.
Cleavage can even be observed on tiny mineral grains making it a very useful property!
Example: Mica is probably the best example as it splits into thin sheets. It is said to have one perfect cleavage.