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Transcript of Minerals
A crystal is a solid in which the atoms are arrange in orderly, repeating patterns.
How Crystals Form
(liquid rock) cools when it reaches the surface of the Earth. When this happens, atoms start loosing energy and start creating compounds. These compounds organize into orderly, repeating patterns.
What do we use Minerals For?
We turn minerals into gems by cutting them and polishing them. Some are worth a lot of money. Some are useful to technology (quartz is used in lasers and in watches.)
Minerals Vs. Rocks
A mineral is a solid crystal compound, made out of only the elements that make that mineral.
Rocks are made out of many different types of minerals.
What is a mineral?
A mineral is a naturally occurring, inorganic solid with a definite chemical composition and an orderly arrangement of atoms.
Minerals occur without help from humans
They are not made out of organic (living) materials
Each mineral has a unique combination of elements
Each mineral has a unique way of organizing its atoms: which is why crystals look different from each other.
Where crystals grow can also affect their shapes: without a lot of room, a crystal won't make it's defined shape but instead look a little bit more like a blob.
There are 6 crystal systems to know about:
Hexagonal - Quartz
Cubic - Pyrite
Tetragonal - Zircon
Orthorhombic - Barite
Monoclinic - Orthoclase
Triclinic - Rhodonite
Water also carries the compounds to form crystals. When this water evaporates, crystals are left behind. Water can also carry TOO MANY compounds, which causes crystals to grow before the water has even evaporated.
The most common rock-forming minerals are called Silicates. These minerals contain Silicon (Si) and Oxygen. The chemical structure of quartz is: SiO2
Some time of minerals we refer to as ORES. A mineral is an ore if it contains a useful substance that can be mined for profit.
For example: we mine hematite for Iron which is used in everything from frying pans to ships.
Because there are so many different types of minerals, it is important to understand the physical properties we use to identify them. Sometimes two different minerals look exactly the same...
We use various "tests" to identify minerals:
1. Hardness: Friedrich Mohs developed a test of hardness that we use to compare minerals to. Calcite is only a three and a diamond is the hardest at a 10.
2.Luster: This is a test for how "shiny" a mineral can be. It's really a measurement of reflecting light.
3. Specific Gravity: This test compares a mineral with the weight of water.
4. Streak: This tests what color the mineral leaves when it's powdered.
5. Cleavage and Fracture: This test looks at the way a crystal breaks. Because of the atoms that grow into certain structures, the crystal will break only certain ways. That is referred to as cleavage. If it just breaks (like glass), we call that fracture.