About the Mineral Calcite
Calcite is a common form of calcium carbonate (aragonite is the crystal form of calcium carbonate) that's well known for its spectacular and varied crystal formations of which there are more than three hundred different types. Calcite has more crystal structures than any other mineral but its crystal habit is often massive which means it exhibits a mass of tiny crystals that occur as one large mass with no visible external shape.
Calcite crystals vary dramatically in size and shape and can occur in almost any colour. In its purest form the mineral calcite is either colourless, very pale or white. Some calcite crystals demonstrate double refraction of light (correctly known as birefringence) meaning that when light passes through them it splits in two giving a double image of the object that's being viewed. Double refraction is widely used in optical applications. The type of calcite that exhibits this unique property is known as optical calcite or Iceland Spar.
During the process of double refraction certain light (unpolarized) travels through the calcite crystal at different speeds and in different directions. As a result one of the rays is bent at an angle or 'refracted' whilst the other remains unchanged. A widely used example is a pencil in a glass of water. At the point where the pencil comes out of the water it appears to be misaligned. That optical illusion is caused by refraction of light. The light only bends at the point where the pencil enters the water but then continues in a straight line.
One of the most common minerals on Earth, calcite forms many rock types including limestone, marble and travertine. It can also be found in caves as stalagmites and stalactites and is the main component in the shells of sea creatures. As they die and fall to the seabed more rocks rich in calcium are created but this process takes place over millions of years. The mineral calcite is so widespread that it can be found in almost every country in the world.
Dog-tooth spar, variety of calcite
The properties of calcite make it one of the most widely used of all minerals and large blocks of limestone and marble have been used in construction for thousands of years. Although today they're seen as a more exclusive material, both are still widely used in the production of cement and concrete.
Mined extensively in Ancient Egypt, white and yellow calcite was used in everything from buildings to vases to the eyes in statues. The Sphinx of Memphis which is believed to have been carved at some time between 1700 and 1400 BC is the largest calcite statue to ever have been discovered. The Great Pyramid of Egypt was once covered with a casing of limestone and it's estimated that 5.5 million tons of the mineral would have been used.
The healing properties of calcite mean that it's widely used in conjunction with alternative therapies such as crystal healing. Beneficial for those who are studying with a particular emphasise on the arts and sciences, calcite is beneficial for motivation, revitalisation and to improve focus and concentration. It amplifies energy and is the perfect crystal to balance and cleanse all of the chakras.
Calcite is a very soft mineral which grades just 3 on Mohs scale of mineral hardness. Pink yellow orange and blue are widely used for lapidary purposes in when used as a gemstone, it tends to be shaped as a cabochon.
The calcite photos featured on this page are courtesy of Stan Celestian (Flickr). The twin crystal at the top of the page is from Brazil, the dog-tooth spar from Mexico. Images are clickable and redirect to the original photos.