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With over 4,000 types of minerals, many physical properties make them distinguishable pieces of matter. To identify minerals and differentiate mineral types, multiple testing methods are put into practice - known as mineral tests. The subject of mineralogy concerns itself with these mineral tests, as well as general reference maps and hydrocarbon exploration.
Minerals are building blocks for rock formation; therefore, mineral testing proves useful and essential in the discovery of metamorphic and rock history, zonation, and geological processes. By using minerals’ properties, mineralogists can decipher mineral types - this is because the properties of minerals are reliant on the crystal structure, the way it’s arranged atomically, and the chemical composition.
Forms of Mineral Testing Explained
Each mineral’s properties can help figure out the sub-class it belongs to. The most common forms of mineral testing are color, streak, luster, hardness, cleavage, density, transparency, and magnetism. Whether the mineral at hand is hard, soft, colorful, dull, chalky, brittle, hard, or powdery, it belongs to a special sub-class.
The color of a mineral is possibly the most obvious identifier. Although this might be easy to figure out at first glance, it is not enough to name a mineral or completely identify its type - many minerals can share similar shades. The same type of mineral can also come in multiple colors and can receive their coloring from chemical impurities.
Streak can sometimes be mistaken for color because it too is a test of color. However, streak tests the powder color of a mineral - this is tested by scraping the mineral on an unglazed plate, allowing a trace of small, powdery fragments to settle. The color of this streak on the plate is the streak of the mineral, which can often differ to the color of the mineral itself. Streak tends to vary less than color, and it is common to find similar color minerals, but streak colors can distinguish them.
A mineral’s luster is determined by the way light reflects off of its surface. There are technical terms to describe this reflection of light. Words such as resinous, earthly, vitreous, and adamantine, describe the non-metallic luster/appearance of a mineral; which can range from physical features of sparkly to dry, and pearlescent to glassy.
The hardness of a mineral relates to its resistance to physical altercation, such as scratching or scraping. Mohs scale helps mineralogists decide the numerical value of a mineral’s hardness; for example, talc, a very soft mineral is at a one hardness, and diamond, a very hard mineral, is at a 10 in hardness.
Minerals will break at different places in their structure; this is known as a mineral’s cleavage. A mineral’s cleavage is vital knowledge for people who cut diamonds, emeralds, and other gemstones. The different breakage on the plane can decide where a mineral can be cut to create a smooth service.
Minerals with more matter in a certain amount of space have a higher density. Density for minerals helps describe how much matter is in a specific amount of space; each mineral type has a characteristic density. The density of a mineral is revealed in the equation: density = mass/volume.
A mineral’s transparency is determined by the way light transmits and travels through minerals; minerals can be opaque, translucent, or transparent. Minerals’ can be nonmagnetic or magnetic - the test used involves a compass or magnet. Special gravity is a ratio that is between the weight and volume
Although these are the most common forms of mineral testing, there are several more that help label minerals in their sub-class, as well as physically distinguish them. Other forms of mineral testing include specific gravity, odor, electric resistance, UV fluorescense, radioactivity, taste, bite test, birefringence, relief, structure, zoning, extinction angle, and general shape.