The composition and structure of each mineral give it properties that are valuable in their use and identification. Some of these make good experiments and demonstrations for the classroom. Beware of tests or results that may yield conflicting information or which may require advanced lab equipment.
- Hardness
- Just about any budding geologist knows of the Mohs Scale of Hardness and that some minerals are harder than others. They may not understand that the hardness depends on the strength of each mineral's chemical bonds, but still, hardness is something easily investigated. Several samples from the Mohs Scale can be easily collected to demonstrate.
- Cleavage
- Cleavage is the way that a mineral will split or break along a flat surface. It is different from the shape of the crystal, though both are actually determined by crystal structure. Cleavage is classeified by the quality of surface produced as well as ease with which it breaks. Not all minerals will produce regular surfaces when broken.
- Fracture
- Those minerals which do not break along regular surfaces may be identified by their fracture rather than cleavage. Fractures may be in many shapes and appeances including conchoidal (smooth curved surfaces), fibrous, or splintery.
- Luster
- Luster is the way a surface of a mineral reflects light. It can be metallic, vitreous, resinous, greasy, pearly, silky, or adamantine.
- Color
- A mineral may have a distinctive color, but can also cause some confusion. The color of a sample may be the property of a pure mineral or a result of impurities within it. An additional investigation of color would include a streak test, where the color of the fine powder left behind when a mineral is scraped across and unglazed tile.
- Specific Gravity / Density
- Simply holding a dense mineral in one hand while holding a far less dense sample of the same dimension in the other hand quickly demonstrates that minerals have different densities or mass per unit volume. Most are too close to measure with the hands or even less sophisticated lab equipment. The specific gravity of a mineral is the standard measure. The number represents the weight of the mineral in air divided by the weight of an equal volume of pure water at 4°C.
- Crystal Habit
- The way a particular mineral grow as crystals are usually named after the geometric shapes they resemble. Their crystal habit is determined by atomic structure and speed with which they grow.
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