Minerals are the building blocks of rocks like dough, flour and milk are the building blocks of bread. Minerals are made up of elements and have a consistent chemical formula. Therefore, they always contain the same quantities of elements. Rocks, on the other hand, are made up of minerals. The different colors in rocks are usually small quantities of varying minerals.
The book How the Earth Works (How It Works) provides a few guidelines for beginning mineral identification.
We looked at the following properties of several different samples.
- Streak Test - What color does the mineral write when scraped on a white tile?
- Specific Gravity - Density of mineral divided by the density of water - The density of water is 1 g/ml^3 at 4 degrees C. To simplify our calculations, we assumed it to be 1 thereby making the specific gravity of the mineral equal to the density in g/m.^3.
- Hardness - Can the following objects scratch the mineral; fingernail-2, bronze coin-3, iron nail-4, glass-5, penknife blade-6, steel file-7, sandpaper-8?
- Acid Test - Does the mineral fizz when a drop of vinegar is dropped on it?
- Color and luster
- Cleavage - Is it flaky? Does it have 90 degree angles, or "rhombic"angles? Is it hexagonal? Is it cubic?
After taking notes on the properties of each mineral we searched the book and the following three websites looking for a match.
Find Minerals by Name
Common Mineral Flashcards
Search Minerals by Properties
One sample I think we identified successfully was quartz with amethyst. I think the green mineral was fluorite? The important part of this activity was the process of identification. Going through the steps the kids definitely became familiar with the important features of minerals.
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