Description
The mineral calcite (also called limespar) consists primarily of the salt calcium carbonate (CaCO3) and is one of the most common minerals in the Earth's crust. Calcium carbonate is formed when soluble calcium ions come into contact with CO2 (carbon dioxide forms a carbonate ion when a positive ion is present in a solution). Calcium carbonate is a poorly soluble salt, causing the resulting CaCO3 to precipitate; this occurs according to the following reaction: Ca2+(aq) + CO32-(aq) → CaCO3(s). Calcite has a trigonal crystal system and belongs to the space group R-3c. A very pure form of calcite is also called bispar due to the birefringence of light in this mineral. It has a rhombohedral structure and is sometimes found as rhombohedral prisms, but it also frequently occurs in other forms, such as scalenohedra, or in fibrous, granular, or compact forms. The crystal structure is primarily a function of temperature, the degree of supersaturation in the crystal's immediate vicinity, and the CO2 pressure. The calcite structure is the stable modification of CaCO3 at room temperature. There is another form, aragonite, which transforms into calcite at 743K. In its pure crystalline form, calcite is clear, colorless, and translucent, but due to impurities (such as copper or sodium salts), it can take on various colors, including gray, blue, violet, green, and even black. It is often also opaque white. The mineral can exhibit both phosphorescence and fluorescence. Its hardness is defined as 3. Calcite is highly birefringent. This optical property was first described by Rasmus Bartholin when the Icelandic form of the mineral, which consists of large, crystal-clear rhombic rhombohedral elements, became available. Christiaan Huygens provided the first explanation with his wave theory of light. Calcite is a common constituent of sedimentary rocks, veins, and deposits in hot springs and caves in karst regions (as stalactites). It is the mineral that forms limestone and thus the most abundant mineral of biological origin. Calcite is the main component of limestone, chalk, and marble, and is also an important component of marl, calcareous sandstone, and limestone. Calcite is responsible for chemical weathering in igneous and metamorphic rocks, creating sedimentary rocks. Calcite is soluble in CO2-containing water under slight pressure. As it falls into the air, rainwater absorbs the gaseous carbon dioxide, making it acidic. This acidic rainwater is capable of dissolving lime. In underground currents, this material can be transported in solution until, upon contact with atmospheric pressure, CO2 escapes and the calcite precipitates. This is how stalagmites and stalactites are formed in caves.
The most beautiful minerals, fossils, and gemstones from Madagascar. Madagascar, officially the Republic of Madagascar and formerly known as the Malagasy Republic, is an island nation in the Indian Ocean, off the southeastern coast of Africa. The nation consists of the island of Madagascar (the fourth-largest island in the world) and numerous smaller outlying islands. It is a renowned diving and swimming destination and is famous for its high-quality gemstones mined from its soil and rocks. We at Timmersgems are proud to say that we are the second-largest importer of Madagascan gemstones in Europe, just behind a French company. Every year, we fill at least three large containers with the finest gemstones, minerals, and buffalo horns. If you take a look in our webshop and showroom, you will find a wide range of labradorite, amethyst, citrine, rose quartz, and many other varieties. We do business with 17 small family businesses on the island. This way, we can guarantee that you will find the best and most beautiful gemstones and minerals. We have also supported these families since the beginning of our business 35 years ago. We have lost our hearts to the island, its people, and its products. It is a wonderful thing to visit the island every year and find the best stones and minerals for you. Madagascar's natural resources include a range of unprocessed agricultural products and minerals, including raffia, fishing, and forestry, and are a mainstay of the economy. Madagascar is one of the world's leading suppliers of vanilla, cloves, and ylang-ylang. Other important agricultural resources include coffee, lychees, and shrimp. Important mineral resources include various types of precious and semi-precious stones, and Madagascar currently provides half of the world's supply of sapphires, which were discovered near Ilakaka in the late 1990s. The island also has one of the largest reserves of ilmenite (titanium ore), as well as significant reserves of chromite, coal, iron, cobalt, copper, and nickel. Several major projects are underway in the mining, oil, and gas sectors, and these are expected to provide a significant boost to the Madagascan economy. These include projects such as Rio Tinto's ilmenite and zircon mining of heavy mineral sands near Tolanaro. Madagascar is a very poor country with abundant flora and fauna. In Madagascar, you can encounter 400 plants and animals that are found nowhere else in the world. The minerals blue celestite, labradorite, and polychrome and ocean jasper are also found only in Madagascar.
