Mineral Properties
- Crystal Form - Outward appearance of the internal mineral structure (unit cell). Need to have adequate space and time to form crystals.
- Luster - Quality of light reflected from the mineral surface. Some examples of subjective qualities or descriptors include vitreous (glassy), resinous, earthy, metallic, and pearly.
- Color - Sometimes diagnostic, but not always.
- diagnostic: pyrite (brassy yellow,) galena (silver)
- Not diagnostic: Quartz (transparent to white to black)
- Some elements can change color
- Streak - Color of the streak left after scratching a mineral on another surface. This is more likely to provide a diagnostic quality of the mineral. A ceramic streak plate is usually used for this.
- Streak color is not always the same color as the mineral itself. (Pyrite is a yellow mineral with a dark green to black streak.)
- Hardness - One of the more useful properties.
- Hardness is measured by the Moh's Scale and given values from 1 through 10, 10 being the hardest.
- Talc
- Gypsum
- Calcite
- Flourite
- Apatite
- K-feldspar
- Quartz
- Topaz
- Corundrum
- Diamond
- Useful comparisons: A fingernail is 2.5, a penny is 3.5, and glass is 5.5.
- Cleavage - Preferred planes of breakage along weak bonds. These can be classified as perfect, strong or weak.
- Specific gravity - Mineral density relative to water
- Quartz - 2.65
- Galena - 7.5
- Gold - 20
- Crystal habit - The general shape of a mineral crystal. These include prismatic, sheet-like, equant, blocky, and botryoidal.
- Other types of diagnostic properties: Magnetic, dissolves in acid, taste, smell, feel, luminescence, and flourescence
Mineral Identification
- Analytical techniques to identify minerals include:
- Hand specimen with hand lens
- Microscope
- Analytical chemistry/wet chemistry
- electron microprobes (ion microprobes)
- X-ray diffraction and X-ray flourescence
- Cathodoluminesence
- Scanning Electron Microscope
- Tunneling Electron Microscope
