barite

الوصف

 
General
Category Sulfate mineral, barite group
Chemical formula
BaSO4
 
 
Crystal symmetry
Orthorhombic
 
Identification
Color Colorless, white, light shades of blue, yellow, grey, brown
Crystal habit
Tabular parallel to base, fibrous, nodular to massive
Crystal system
Orthorhombic

Cleavage
Perfect cleavage parallel to base and prism faces: {**1} Perfect, {**0} Perfect, {**0} Imperfect
Fracture
Irregular/uneven
Tenacity Brittle
Mohs scale hardness **3.5
Luster
Vitreous, pearly
Streak
White
Diaphaneity
transparent to opaque
Specific gravity
4.3–5
Density
4.*8 g/cm3
 
 
 
Fusibility
4, yellowish green barium flame
Diagnostic features white color, high specific gravity, characteristic cleavage and crystals
Solubility
low

general
Baryte, or barite, (BaSO4) is a mineral consisting of barium sulfate. Baryte itself is generally white or colorless, and is the main source of barium. Baryte and celestine form a solid solution (Ba,Sr)SO4
Uses
*- Well drilling fluids Drilling fluids are designed to cool the drill bit, lubricate the drill stem, seal the walls of the well hole, remove cuttings, and confine high oil and gas pressures by the hydrostatic head of the fluid column. A high specific gravity fluid is required to maintain sufficient hydrostatic pressure to control hydrocarbon release and prevent gushers and fires. Barite is uniquely suited as the weighting agent because it is heavy, chemically inert, and nonabrasive. The deeper the hole the more barite is used, because hydrocarbon pressure rises strongly with depth below about ***0 meters. In most drilling fluids barite is the major ingredient by weight percent. used as a weighting agent for drilling fluids in oil and gas exploration to suppress high formation pressures and prevent blowouts. As a well is drilled, the bit passes through various formations, each with different characteristics. The deeper the hole, the more barite is needed as a percentage of the total mud mix. An additional benefit of barite is that it is non-magnetic and thus does not interfere with magnetic measurements taken in the borehole, either during logging-while-drilling or in separate drill hole logging. Barite used for drilling petroleum wells can be black, blue, brown or gray depending on the ore body. The barite is finely ground so that at least *7% of the material, by weight, can pass through a ***-mesh (**-μm) screen, and no more than *0%, by weight, can be less than 6 μm diameter. The ground barite also must be dense enough so that its specific gravity is 4.2 or greater, soft enough to not damage the bearings of a tricone drill bit, chemically inert, and containing no more than **0 milligrams per kilogram of soluble alkaline salts.

*- Glass In glassmaking barite saves fuel by reducing the heat-insulating froth on the melt surface.It also acts as an oxidizer and decolorizer, making the glass more workable. It reduces seeds and annealing time and improves glass toughness, brilliance, and clarity.
*- Coatings Paints and primers represent the largest use for filler-grade barite. High-brightness micronized barite is used as an extended to provide the weight that customers equate with quality and because of its low binder demand, which allows high loadings. Blanc fixe is used where a finer particle size is needed for denser packing of the paint film, as in premium metal primers, and
to provide resistance to corrosion by acids and alkalis. Despite their high brightness barite and blanc fixe have poor hiding and tinting strength because they are close to the refractive index of binders.

They function instead as extenders and spacers, keeping the pigment particles separated and uniformly disseminated to optimize light scattering

*- Polymers Finely ground barite is used in rubber, where its weight, inertness, isometric particle shape, and low binder demand are advantageous. It has little effect on cure, hardness, stiffness, or aging. It is used in acid-resistant compounds, in white sidewalls for tires, and in floor mats. Blanc fixe fine enough to be semi reinforcing is used to provide the same compound softness and resilience as barite but better tensile strength and tear resistance. Barite is used in PVC and polyurethane foam backings for carpeting and sheet flooring
because of its ability to form dense coatings due to its high specific gravity and its ability to be used at high loadings.

*- Because barium sulfate is insoluble and opaque to X-rays, blank fixe meeting pharmacopeia specifications is used as an indicator in medical X-ray photography.
*- Natural barite is used in concrete for the construction of facilities handling nuclear materials because it absorbs gamma radiation.
*-Micronized white barite and blanc fixe are used as fillers and extenders, primarily to add weight, in bristolboard, playing cards, and heavy printing papers. Blanc fixe is used in the base coat of photographic papers to supply an inert substrate for the silver halide emulsion coat. Finely ground (***5 mesh) barite is used as an inert filler in brake linings and clutch plates.

*- Historically baryte was used for the production of barium hydroxide for sugar refining, and as a white pigment for textiles, paper, and paint.