Kalsit

This calcite is carved into various figures, and nearly every child in America has one or two animal figures made from Mexican agates. Carved vases, bookends, plates, ovaries, pyramids, and trinkets are all very popular. The quartz type is slightly different and more valuable than agate (used in jewelry) and has a black or white belt. The best way not to confuse the two is to call it Mexican akiki. Mexican agate has multiple orange, yellow, scarlet, tan, brown, and white-colored bands and is like woven marble. The carvings are extremely attractive and precious.

Because it is so abundant and spread over such a wide area, it is not surprising that it can be so diverse. Calcite crystals are exactly a thousand grained, based on structures such as the main shapes, positive and negative rhombohedrons, steep, partially, or weakly inclined rhombohedrons, various scalahedrons, prisms. It can form different structures. More than 300 crystal forms have been identified in calcite, and they can combine to form thousands of different crystals. Calcite also forms twin species that are popular with collectors. There are also phantoms that contain crystals, color variations, and rare associations. Simply put, there is no end to the diversity of calcite.

BThere are many types of calcite, and it is not possible to describe all of them. However, there are several prominent species. Probably the best-known type of calcite is the most common form,the scalenohedron or ‘’Dogtooth Pole’’as it is sometimes called. This type of binary pyramid or dipyramid but can also differ markedly. The scalenohedron point is very sharp and, as the name suggests, looks exactly like a dog’s tooth. Beautiful clear colorless or amber-orange specimens are considered classics of the genre, with leading examples being Pugh Quarry, Ohio; It comes from Cornwall, England, and Elmwood, Tennessee. But this species is found all over the world.

Not necessarily a type of calcite, cave formations are definitely one side of the calcite story. Calcite is the main mineral component in cave formations. Calcite is the basis of stalactites and stalagmites, cave veils, cave pearls, soda cans, and many more cave formations, and millions of visitors enjoy watching them in the underground caverns. The fact is that calcite was easily dissolved in the formation of these formations. The limestones found in the cave ceiling have been dissolved by acidic underground waters over the years and infiltrated down into large and deep caves. In fact, large and deep caves themselves may have been formed by the dissolution of limestone-rich areas. When water enriched with calcite enters a moisture-dry cave, the water begins to evaporate and at the same time, the calcite it contains begins to precipitate. As a result, the deposited calcite is usually extremely pure and is colored if it contains traces of iron or other foreign materials.

Veined agate of Mexico is a type of calcite often used in ornaments.

This calcite is carved into various figures, and nearly every child in America has one or two animal figures made from Mexican agates. Carved vases, bookends, plates, ovaries, pyramids, and trinkets are all very popular. The quartz type is slightly different and more valuable than agate (used in jewelry) and has a black or white belt. The best way not to confuse the two is to call it Mexican akiki. Mexican agate has multiple orange, yellow, scarlet, tan, brown, and white-colored bands and is like woven marble. The carvings are extremely attractive and precious.

Another type is called the “Iceland Pole”. It consists of extremely clear pieces and is completely colorless (as ice). It was first discovered and named after Eskifjor, after calcite was found in basalt caves in Iceland. Iceland poles are plentiful and inexpensive in rock stores around the world and are also extremely popular with children. Most of the Iceland poles today come from Mexico. Iceland poles exhibit classical calcite cleavage, the rhombohedron. During the second world war, Iceland poles were minerals of extremely strategic importance. These were used as optical equipment (sight) by bombers and artillery. The Iceland poles show the feature of calcite, which is called a double fracture, in the best way.

• Double refraction occurs when light enters the crystal and due to the unique optical properties of calcite, the beam is split into fast or slow beams. These two beams come out of the crystal and bend in two different angles (known as refractive angles) because the angles of the beam are split. affected by the speed of the beam. A person looking into the crystal will see everything as two objects. The best way to see double refraction is to lay the crystal on a flat surface or with written words (the result will be two lines or two words). Rotating the crystal will show the direction parallel to the C axis in the crystal when the words become whole again. By comparison, the direction perpendicular to the C axis will have the widest separation. The extremely high refractive index of calcite, which causes double refraction to be easily seen, is also responsible for the parasitic colors (pastel rainbow colors) seen in calcite with small particles.

Fluorescence, phosphorescence (burning), thermoluminescence (luminous with temperature), triboluminescence are other important properties of calcite. Although not all specimens show these properties, some do so well, and in some cases they are detectable. The most notable case for fluorescence occurs in Franklin, New Jersey. Here, a large amount of calcite is stored in a small amount of manganese and is exposed to UV light. radiates like a bright red color. Some of the Mexican Iceland poles glow a beautiful purple or blue color, and these unique specimens also have phosphorescence properties when the UV light source is withdrawn. That being said, triboluminescence is a feature that can be seen in many examples but is extremely difficult to prove. This is when the samples are under pressure in a dark room, the sample is expected to glow.

The best feature of calcite is the acid test. Why? Because, when cold acid is poured on the sample, calcite will always foam up. Even the cement in the sandstones will foam up to ensure the work of the geologists working on the determination of the cement mineral. The reason for foaming is given in the formula below.

CaCO₃ + 2H(+)                 Ca(+2) + H₂O + CO₂ (gaz)

The carbon dioxide gas was expelled as balloons and the calcium was dissolved in the residual water. Any acid can give these results, but diluted hydrochloric acid or vinegar are the 2 recommended acids for this test. Other carbonates, such as dolomite or siderite, do not react as readily with these acids as calcite does, making it extremely useful for separating minerals.

On the other hand, the bond between calcite and carbon dioxide is quite complex.

When marine organisms such as coral and algae decalcify their shells, they draw carbon dioxide from seawater. It’s a coincidence for us, just as carbon dioxide is found as a greenhouse gas and contributes to the “greenhouse effect”. Environmentally, calcite is very important and has been extremely important in the successful development of our planet in the past. Due to the removal of carbon dioxide from seawater, this biological activity allows most of the carbon dioxide in the air to dissolve in seawater and therefore acts as a carbon dioxide filter for the planet. Environmentalists are trying to determine what the “greenhouse gas effect” would be like if this activity is increased by human intervention. A significant portion of the precipitated calcite found in seawater is strictly inorganic, but the exact proportion that contributes to this is not well known. Calcite and other minerals are extremely important in the world’s ocean ecosystem.

Calcite is not just a calcium carbonate mineral. There are at least three minerals, or what can be called all three phases of CaCO3. Aragonite and Vaterite, together with calcite, are polymorphs (Latin for “multistructure”). They all have the same chemical properties, but differ in symmetry and crystal structures. Aragonite is orthorhombic ,Vaterite hexagonal and Calcite trigonal is trigonal. Aragonite is a common mineral, but in most environments and under heat and pressure, calcite is more stable than aragonite. On the other hand, vaterite is extremely rare. Over time, aragonite will turn into calcite, and calcite pseudomorphs (false shape) will not be common after aragonite.

Indeed, calcite is one of the best collectible minerals. It has many interesting formations and a wide variety of colorful and beautiful specimens to collect. Recognition of calcite is fairly easy using rhombohedral slits, acid reaction, and double fracture, and all these properties make calcite a great example for classrooms. If calcite is not an important mineral on a specimen, it becomes just an accessory to other fine minerals and enhances their impressiveness. With its many different formations, colors, and combinations, calcite is a mineral that a collector will never find all these features in another mineral.

PHYSICAL PROPERTIES OF CALCITE :

• Color is extremely diverse, but usually white or colorless or light shades of yellow, orange, blue, pink, scarlet, brown, green, black or gray. From time to time, it is iridescent.
• The Gloss is dull in large formations, such as glass in resins.
• Transparency crystals from transparent to translucent
• The Crystal Systemis trigonal; 3 2/m bar
• Crystals are extremely diverse in structure, usually in any possible trigonal form. Among common calcite crystals; scalenohedron, rhombohedron, hexagonal, prism and pinacoid. Combinations of these and over three hundred other formations can form multiple crystal structures, but they are always trigonal or pseudo-hexagonal. Doubling is frequent and causes blocky V shapes, right angled prisms, heart shapes, and pyramid shapes within crystals. A notch in the middle of a bidirectional scalenohedron is definitely a sign of double crystallization. Weak duplication, resulting in striated cleft surfaces, is also seen. Many minerals other than pseudomorphs are known, but they are easily recognized as calcite. Large, fibrous, concretized, pendulous, nodular, granular, radial, branched, granular or layered etc.
• The slits, are perfectly three-sided forming rhombohedrons.
• Fracture is conchoidal..
• Hardness is 3. (Only on basal pinacoidal surfaces, calcite has a hardness of less than 2.5 and can be chipped with nails.)
• The average specific gravityis 2,7.
• The lines are white..
• Other Properties: refractive index is between 1.49 and 1.66 and causes a significant double refractive effect (if a clear crystal is placed on a single line, 2 lines can be obtained), easily foams with diluted acids and fluorescence, phosphorescence (burning), thermoluminescence (luminescence) and triboluminescence.
• Associated minerals are plentiful but generally include the following classical associations;
  Fluorite, quartz, barite, sphalerite, galena, celestite, sulfide, gold, copper, biotite, zeolite, many metal sulfides, other carbonates and borates and many more minerals.
• Notable formations: Pugh Quarry, Ohio, Rosiclare, Illinois; Franklin, New Jersey; Elmwood, Tennesee, Brush Creek and other states of Missouri, Wisconsin, Kansas and Oklahoma, USA; Andreasburg, Harz Mountains and Saxony, Germany; Guanajuato, Brazil; Cornwall, Mexico Duhram and Lancashire England; Mumbai region of India Eskifjord, Iceland many parts of Africa and many more places in the world.
• Best signs: Crystal structure, acid sensitivity, multiplicity, hardness, double fracture and especially clefts.