1. Color:
* Mineral Color: This can be a helpful starting point, but can be misleading as impurities can affect color significantly.
* Streak: The color of a mineral's powder when rubbed against a streak plate. This can be more reliable than the mineral's overall color.
2. Luster:
* Metallic: Shiny, like metal.
* Non-metallic: Includes:
* Vitreous: Glassy.
* Resinous: Like resin.
* Pearly: Like a pearl.
* Silky: Like silk.
* Dull: No shine.
* Earthy: Like soil.
3. Hardness:
* Mohs Hardness Scale: Measures a mineral's resistance to scratching. A harder mineral will scratch a softer one.
* Fingernail (2.5), Copper Penny (3.5), Glass (5.5), Steel Knife (5.5) are useful reference points.
4. Cleavage & Fracture:
* Cleavage: Tendency to break along smooth, flat planes. Described by the number of cleavage planes and their angles.
* Fracture: How a mineral breaks when not along cleavage planes. Examples include:
* Conchoidal: Shell-like, curved fracture.
* Uneven: Rough, irregular fracture.
* Splintery: Like wood.
5. Crystal Form:
* Habit: The typical shape of a mineral crystal.
* Crystals: Minerals with a well-developed, geometric shape.
* Crystalline: Has a definite internal arrangement of atoms, even if the crystal shape is not obvious.
* Amorphous: Lacking a definite internal structure.
6. Specific Gravity:
* Density: How heavy a mineral is for its size. Specific gravity is the ratio of the mineral's density to the density of water.
7. Magnetism:
* Magnetite: Attracted to a magnet.
8. Other Properties:
* Taste: Some minerals have a distinct taste.
* Smell: Some minerals have a characteristic smell, especially when scratched or rubbed.
* Feel: Some minerals feel smooth, oily, or gritty.
* Fluorescence: Some minerals glow under ultraviolet light.
* Radioactivity: Some minerals are radioactive.
9. For Rocks:
* Texture: The size, shape, and arrangement of mineral grains within a rock.
* Foliation: The alignment of mineral grains in a rock, often caused by pressure.
* Grain Size: The size of the mineral grains in a rock.
Remember: Identifying rocks and minerals requires practice and experience. Using a combination of these physical properties will help you narrow down the possibilities and make a more accurate identification.
