This is the mineral Halite. It’s commonly called Rock Salt, or simply Salt, and is usually clear or white with a vitreous, or glassy, luster. Some specimens faintly exhibit a yellow, red, or even bluish tint. It’s a relatively soft mineral, ranking 2.5 on Mohs hardness scale. Thus, Halite can scratch Gypsum, which is ranked 2, but not Calcite, which is ranked 3. When drawn across a black ceramic streak plate, it easily produces a vivid white streak. With a specific gravity between 2.1 to 2.6, it feels relatively light in your hand. Halite exhibits perfect cubic cleavage. This is especially apparent when striking a large sample with a rock hammer because small cubes spall from the break. You can also see this cubic characteristic when examining Halite using a hand lens or a microscope, as many individual crystals appear as cubes. Halite’s chemical composition is NaCl, which is Sodium Chloride. Since Halite is composed of just 2 elements, one of which belongs to Group 17, also known as the Halogens, on the Periodic Table, this mineral belongs to the Halide chemical family. It’s difficult to overstate the importance of Halite because it’s an essential mineral for maintaining human health and society. Our cells depend on Sodium, normally obtained via ingesting Salt, to regulate osmotic pressure, which is the movement of water across cell membranes. Sodium is essential for our nervous system, muscles, and kidney functions. Sodium also plays a critical role in chlorophyll production, without which plants could not conduct photosynthesis. Throughout human history Salt has been used as a source of currency, as a food preservative, and as a disinfectant. During winter months, massive volumes of Halite are spread across roads and sidewalks to melt snow and ice.