In nature, minerals occur as inorganic solids with defined chemical compositions as well as crystalline lattice structures. All minerals have unique physical and chemical characteristics that make them different from each other. While the chemical formula and the crystal lattice of a given mineral can be determined in a laboratory setup, it is possible to determine the identity of a mineral using its physical properties (Carmichael, 2017). Noteworthy, the physical properties of a mineral, which refers to the way in which a mineral appears, result from the inner chemical properties of that specific mineral (Ha et al., 2017). All minerals are identified using their physical properties. In essence, there is a relationship between what a mineral looks like and its physical properties.
Color is the most common characteristic that mineralogists look for when identifying a given mineral. Nevertheless, color is the least effective method of identifying minerals since many different minerals can have the same color. In the same manner, a specific mineral can assume more than one color (Ha et al., 2017). For instance, several minerals, such as epidote, olivine, and actinolite, are green in color (Carmichael, 2017). In the same manner, quartz can be pink, smoky, yellow, or purple, depending on the level of impurity in its chemical structure. Similar to other objects, minerals reflect, emit, and absorb light of different wavelengths, which is then perceived by the human eye and interpreted in the brain as a specific color (Carmichael, 2017). Depending on the state of oxidation, iron can produce more than one color, mostly red, black, or green.
The crystal form is one of the most effective ways of determining the color of a given mineral. In mineralogy, the internal atomic structure determines the external shape of a mineral crystal. The crystal form of a mineral is defined by the angular relationship between the faces of its crystals. For instance, halite and pyrite are salts with cubic forms, while tourmaline has a prismatic form. Minerals like malachite and azurite are both copper ores that do not have regular crystals but appear amorphous.
Hardness is a common characteristic of the objects used to determine a given mineral’s identity. The hardness of a substance is defined by its resistance to scratching and is the measure of the length of the structure of its internal crystals. The Mohs’ scale, developed by Fredrick Mohs in 1883, is a diagnostic tool that measures the degree of hardness of minerals. The scale runs from 1 to 10 depending on the level of hardness, wherein 1 indicates the softest while 10 indicates the hardest (Carmichael, 2017). The bonding of a crystal structure determines the degree of hardness of a mineral. In addition, the bonding of a crystal structure differs with directions, implying that a given mineral’s hardness can differ with crystallographic directions. As an example, the hardness of kyanite on Mohs’s scale is 4.5 when considered parallel to the chains of silica tetrahedra is 6.5 when considered in the direction of perpendicular to the chains (Ha et al., 2017). Consequently, hardness cannot be used as the sole diagnostic approach for minerals.
Minerals can be magnetic or non-magnetic depending on the elements that make their structure. For example, minerals with copper, nickel, cobalt, iron, and chromium can have magnetism because the elements tend to have magnetic fields in nature. In nature, minerals can be diamagnetic, paramagnetic, or ferromagnetic, depending on how they react to a magnet. Diamagnetic refers to the slight repulsion or tendency to move towards the regions of the weaker magnetic field (Carmichael, 2017). Paramagnetic characteristic refers to slight attraction in which materials tend to move towards regions of strong magnetic fields. Ferromagnetism is the tendency to have a strong attraction towards regions of strong fields.
References
Carmichael, R. S. (2017). Magnetic properties of minerals and rocks. In Handbook of physical properties of rocks (pp. 229-288). CRC Press.
Ha, W. N., Nicholson, T., Kahler, B., & Walsh, L. J. (2017). Mineral trioxide aggregate—a review of properties and testing methodologies. Materials, 10(11), 1261. Web.