CALCITE

Calcite is a common carbonate mineral, which forms many types of rock; including limestones, marble, travertines, and marls, as well as stalactites and stalagmites within caverns and cave systems. It crystalizes at low temperatures and in a wide variety of shapes and colors, often forming large, twinned scalenohedral crystals. Acute scalenohedral crystals are often referred to as "dogtooth spar", while the rhombohedral form is occasionally referred to as "nailhead spar". Calcite is best recognized by its effervescent reactivity with acids, such as vinegar. Additionally, if pressure is applied, or if it is dropped, it will naturally split along its cleavage points into smooth-surfaced, rhombohedral pieces. Calcite is often transparent to opaque and may infrequently show phosphorescence or fluorescence. Interestingly, a rhombohedral form of optically transparent calcite, sometimes called "Iceland spar", was often used by the Vikings, where it served as a navigational tool for tracking the sun on cloudy days. Calcite is found world-wide, with the most notable mining operations occurring at the Calcite Quarry in Michigan, USA. The Calcite Quarry is the largest carbonate mine in the world and has been in production for more than 100 years. The largest documented single crystal of calcite formed in Iceland, where it measured roughly 20ft × 20ft × 10ft, and weighed nearly 250 tons, or about 551,000 pounds!

CALCITE HISTORY AND USES

Historically, the many uses of calcite have been well-documented; for instance, Ancient Egyptians carved many items out of calcite, often in depiction of their goddess Bast, whose name directly contributed to the term alabaster, due to its close association. Many other cultures have used calcite for carved objects and applications, with the most colorful variations garnering the most attention. Interestingly, a rhombohedral form of optically transparent calcite, sometimes called "Iceland spar", was often used by the Vikings, where it served as a navigational tool for tracking the sun on cloudy days. The Vikings realized that a very pure crystal of calcite can split a beam of sunlight into dual images, as the polarized light slightly deviates from the main beam. By observing the sky through the crystal, the rings of polarized light that surround the sun can be easily viewed, even under cloudy skies. Identifying the sun's location gave these early seafarers a reference point for navigating the oceans. More recently, during WW11, high-grade optical calcite was widely used as a polarizer in bomb sights and anti-aircraft weaponry, and it is still applied in many optical instruments in use today. Currently, the most common uses of microbiologically precipitated formations of calcite are for soil remediation, soil stabilization, and concrete repair.

In the animal world, calcite is often the primary component of the shells of marine organisms; such as plankton, brachiopods, echinoderms, and certain bivalves such as oysters. Fascinatingly, Trilobites, which became extinct during the end of the Permian period over 250 million years ago, had unique compound eyes that were composed of optical calcite crystals, which formed their lenses. Additionally, it makes up a substantial portion of all species of birds’ eggshell.

CALCITE METAPHYSICS

Metaphysically, calcite is said to increase and amplify energies of emotional healing and spiritual awareness. It is also believed to be a spiritual cleanser that facilitates a positive shift in personal perspective. A crystal of renewal and change, calcite is said to aid its user in finding an effortless flow of personal fulfillment and everyday wonder. Physically, calcite is said to aid the body with calcium absorption, creating strong and healthy bones. It is also said to aid the body with intestinal disease and ulcers.