Celestine Geode (2) Crystals Raw Minerals Stones Rocks Collecting

Celestine Geode Extra quality 4052 gr - cm 16.5 x 15 x 12.5 Crystals Raw Minerals Stones Rocks for Collection, only a piece, as in photos.

A Geode is a secondary geological formation within sedimentary and volcanic rocks. Geodes are hollow, loosely spherical rocks in which masses of minerals, which may include crystals, are isolated. Geodes are formed from masses of magma whose non-homogeneous and very slow cooling inside allows the minerals to arrange themselves in an orderly manner according to the crystalline lattice. In fact, they represent gas bubbles variously modeled by the greater or lesser flow of the magmatic liquid. The lower the viscosity of the liquid, the more elongated can be the shape of the geode whose sharpest part coincides with the direction of flow.
Groups of "grown" crystals can develop on the internal walls of these geodes thanks to the particular chemical composition and the relatively high temperature of the hydrothermal fluids percolated through the rock. Most geodes contain clear quartz crystals, while others have purple amethyst crystals. Still others may have bands of agate, chalcedony or jasper or crystals such as calcite, dolomite, celestite, zeolites, selenite, carbonates and sulphates, etc. The banding and coloration of the geode are the result of varying impurities.
It can vary in size from a few centimeters up to, in exceptional cases, a few metres, real caves.
Geodes come from Brazil, Uruguay, Namibia, Mexico, United States. Geodes are also abundant in the Mendip Hills in Somerset, England, where they are known locally as "potato stones".

Celestine or Celestite is a mineral consisting essentially of strontium sulphate (SrSO4), bipyramidal rhombic, belonging to the homonymous group.
It has a hardness of 3-3.5 on the Mohs scale and a density of 3.9 g / cm3. It is an important strontium mineral.
It comes from the Latin term caelestis (light blue), referring to the color of the crystals.
The crystalline habit occurs in colorless or slightly bluish tabular crystals, usually in limestone and sedimentary rocks, associated with gypsum, anhydrite, rock salt and sulfur. It is also found with other clothes: prismatic, acicular, lamellar (red, white or blue), fibrous, coarse, massive granular.
Celestine can have hydrothermal origin, in association with galena and blende, or evaporitic sedimentary due to the evaporation of brackish water in association with sulfur, gypsum, aragonite, chlorides and other typical minerals. It can also be found in sedimentary rocks, especially limestone. In the sulphates and in the salt deposits. In magnificent crystallized druze it is found, associated with sulfur, in its deposits in Sicily and Romagna (Italy).
In nature it generally occurs in elongated prismatic crystals, sometimes tabular, colorless or milky white, yellowish, blue, in radiated or parallel, massive or concreted aggregates. Celestine is heavy, semi-hard and brittle. The mineral is weakly soluble in water and acids and colors the flame carmine red. It also exhibits thermoluminescence and is fluorescent under ultraviolet rays in yellow and white-blue.