SILLIMANITE
Introduction
The professional English vocabulary is: sillimanite. In the crystal structure, two tetrahedrons [SiO4] and [AlO4] are alternately arranged along the Z axis to form an aluminosilicate [AlSiO5] double chain. The crystal is columnar and needle-shaped, and the aggregate is fibrous. White, grayish white, can also be light brown, light green, light blue, glass luster or silky luster, the board surface is completely cleavable. Mohs hardness 7.5, specific gravity 3.23 ~ 3.27.
Refractive index: 1.66~1.67, birefringence: 0.010. The sillimanite is a typical high-temperature metamorphic mineral. It is formed by the metamorphism of high-altitude argillaceous rocks and is produced in crystalline schist and gneiss. It is also found in the contact zone between the aluminum-rich rock and the igneous rock.
The sillimanite is a typical high-temperature metamorphic mineral. It is formed by the metamorphism of high-altitude argillaceous rocks and is produced in crystalline schist and gneiss. It is also found in the contact zone between the aluminum-rich rock and the igneous rock. When the stone is heated to 1300 ° C, it becomes mullite and can be used as a high-grade refractory material.
It is an important non-metallic mineral material with high temperature thermal stability, folding resistance and slag resistance. It is widely used in advanced refractory materials, acid-resistant materials, technical ceramics, In the field of silicon-aluminum alloy and artificial mullite, the bright color can be used as a gemstone raw material, and the single crystal can be ground into a faceted gemstone, and the domestic market is mostly a striated cat's eye. In addition, the sillimanite stone has low porosity, corrosion resistance and abrasion resistance, and is an aggregate of denture casting, bone graft and bone grafting plate.
Genetic and physical properties
Cause
The sillimanite is a metamorphic mineral produced in the aluminous rock in the high temperature contact metamorphic zone. For example, in the northwest of Beijing Zhoukoudian, the muddy cement of the Permian Hongmiaoling sandstone formed a sillimanite stone after thermal deterioration with the granite. World-famous origins include Mardo in Czech Bohemia, Fassa in Tyrol, Austria, Minas Gerais in Brazil, and New Hampshire in the United States.
The sillimanite is a typical metamorphic mineral with a wide distribution. Common in igneous rocks (especially granite) and contact zones rich in aluminum rocks and areas where schist and gneiss develop. The sillimanite in the black mica shale shale and the scorpion sapphire gneiss is usually due to the decomposition of biotite or the early formation of andalusite. The eve stone often coexists with andalusite, kyanite, corundum, cordierite and the like. In the weathering process, the sillimanite stone is very stable, so it is common in impact sand mines, residual layers and slope layers.
Physical properties
The color of the eve stone is white, gray or light green, light brown, etc.; glass luster. The cleavage is complete, and the cleavage plane is double-stranded in a parallel structure. Hardness 6.5 ~ 7.5. The relative density is 3.23 to 3.27. Thermal analysis: heating to 1545 ° C, the sillimanite is converted to mullite and quartz.
Mullite is an important ceramic material. Its structure is the same as that of the stellite stone, but there is excess Al→Si entering the tetrahedral double chain. In order to balance the electricity price, some O2-absences, ie mullite, are produced. The chemical formula is: Al4+2xSi2-2xO10-x, and x is the number of O2-absent.
Crystal chemistry
Molecular formula Al2[SIO4] O, theoretical composition (wB%): SiO2 (37.1), Al2O3 (62.90). Al in andalusite can be replaced by Fe (≤9.6%) and Mn (≤7.7%). Kyanite may contain Cr (≤12.8%), and often contains Fe (1~2%) and a small amount of Ca, Mg, Fe, Ti and the like. The sillimanite composition is relatively stable, and a small amount of Fe replaces Al, and may contain trace amounts of Ti, Ca, Fe, Mg, and the like.
Structural form
It belongs to orthorhombic system, in which a0=0.744, b0=0.760, c0=0.575, the crystal is long column or needle. There are streaks on the cylinder of the crystal strip. The aggregate is radial or fibrous. Sometimes it is hairy and exists as an inclusion in quartz or feldspar crystals.
The hairy ceremonial stone is called a thin stone. This needle-like crystal form of sillimanite is related to the presence of [SiO4] and [AlO4] double chains and [AlO6] octahedral chains in its structure.
The basic structure is composed of [SiO4] and [AlO4] tetrahedrons alternately arranged along the c-axis to form an [AlSiO5] double-strand; the double-stranded chain is connected by [AlO6] octahedron, and the [AlO6] octahedron is co-edge-joined into a chain.
The four corners and the center of the unit cell projection surface, 1/2 of Al is a four-time coordination. The structural characteristics determine that the sillimanite has a c-axis extended acicular, fibrous crystal morphology and cleavage in the parallel c-axis direction.
Identification characteristics: It can be identified according to its rod shape, needle crystal form and production in contact metamorphic belt and metamorphic rock.
Microscopic feature
Under the microscope, inclusions such as rutile, spinel and biotite can be seen. A group of fibrous inclusions arranged in parallel are visible in the cat's eye, and the cat's eye in Sri Lanka is caused by the arrangement of fibrous perilla pyroxene and some rutile needles. The sillimanite may also exhibit a cat's eye effect in a fibrous aggregate.
Industrial applications
Application overview
The sillite stone is mainly used for the manufacture of high-aluminum refractory materials and acid-resistant materials, and is used in technical ceramics, insulators for spark plugs of internal combustion engines, cast steel crucibles, pyrometers, and silicon-aluminum alloys for aircraft, automobiles, trains, and ship parts. The bright color of the eve stone is the raw material of the gem.
Compared with the world's advanced countries, the development and application of China started relatively late. In the 1960s, the porphyry of the Baiyun mother sill line, which was produced in Fujian Putian, was directly cut into refractory materials of various shapes and sizes and sold to the province and abroad.
In the late 1970s, due to the construction of Shanghai Baosteel, the foreign party proposed the use of three stones including the sillite stone, which promoted the development and application of the Chinese sillimanite mineral. At that time, Baosteel mainly applied sillimanite to high-alumina bricks in the soaking furnace, the key parts of the heating furnace and the 300-ton steel corundum corundum.
Applications
1.Compound sill stone prefabricated whole crucible This utility model discloses a compound sillite prefabricated whole crucible, which is characterized by using white corundum, fused mullite, corundum powder, zircon and sillimanite powder. The crucible is pre-formed, the inner surface of the crucible is a spherical bottom cylinder, and the outer surface is cylindrical. According to the utility model, the prefabricated crucible comprises 0.3 to 5 tons of acidic, alkaline and neutral antimony, the furnace can be used up to 40 furnaces, the safety factor is greatly improved, the process cycle is greatly shortened, and the raw material cost is greatly reduced.
The invention relates to a squash stone refractory ball with a diameter of 60-70 mm and a production method thereof, and is mainly suitable for heat exchange of the upper part of a ball-type hot blast stove of a blast furnace of less than 500 m3. material. The refractory ball is made by reasonable mixing, uniform kneading, semi-dry pressing, and firing. The refractory ball has the advantages of good thermal shock resistance, large heat capacity, corrosion resistance, no sticking between the ball and the ball, not easy to burst, peeling off, and can improve the heat exchange efficiency of the hot blast stove, and is a ball-type hot air of a blast furnace of 500 m3 or less. The ideal heat exchange material in the upper part of the furnace.
3. Refractory ball combined with sillimanite and andalusite fine powder The present invention relates to a refractory material, in particular to a refractory ball in which a combination of sillimanite and andalusite fine powder is combined. In terms of weight percentage, the raw material contains 40-60% of high aluminum material, 1~5% of gasified SiO2 fine powder, 2~8% of sillimanite, 2-14% of andalusite, 10-30% of pyrophyllite, white dry clay 8 ～15%, additional admixtures containing 2 to 8% of the total weight of the raw materials. The fire resistant ball of the present invention has the following advantages:
(1) The high temperature creep rate is reduced to 0.3% or less under the condition of 0.2 MPa × 1400 ° C × 5 h.
(2) High compressive strength, reaching 25,000 N/ball.
(3) The high temperature resistance is good. Under the high temperature of 1500 °C, the sphere does not deform and does not soften.
(4) The product has a long service life, and the initial service is more than 5 years, which saves a lot of maintenance costs and has good economic and social benefits.
Gem value
Cat eye stone: English name sillimanite cat’s eye. It is a more common gemstone with cat's eye effect, mainly from India and Sri Lanka. It is composed of a fibrous aggregate of stellite stones. Often grayish green with black inclusions.
The inclusions have been identified as magnetite and hematite. The cat's eye band is usually wide and fuzzy, and the effect is poor. Occasionally, it has a beautiful yellow-green color. The cat's eye band is very clear, and it is difficult to distinguish it from the golden emerald cat's eye. However, the celestial stone cat's eyes have a lower refractive index and a lower relative density, which can be identified.
Identification of stellite stone and similar gemstones
(1) Identification of sillimanite and similar gemstones
The taupe sillimanite has a similar appearance to the smoky quartz and can be distinguished by its high refractive index and density. The sillimanite fibrous inclusions are usually clearly characterized and can be confused with grapevines but can be distinguished by refractive index and density.
(2) Identification of the scorpion stone cat eye and similar gemstones
The eve of the stone cat eye is common, usually grayish green, brown, gray, translucent to opaque, rare transparent, magnified observation visible fibrous structure or fibrous inclusions, eye line diffusion, inflexible. The measured refractive index is 1.66. Under the polarizer, it can be seen as four or four dark or collectively polarized.
1. Tourmaline (tourmaline) cat's eye
The tourmaline cat's eye is usually blue, green, and pink. The transparency is higher than that of the celestial stone cat's eye, and the thick tubular body is visible to the naked eye. Point measurement refractive index 1.64. Under the polarizer, it is often four bright and four dark.
2. Apatite cat's eye
The apatite cat's eye is usually yellow-green and brown-green, and the thin tubular inclusions are enlarged, and the eye line is obvious and flexible. The refractive index was measured at 1.63 or 1.64. The characteristic spectrum was 580 nm double line. Under the polarizer, it is often four bright and four dark.
3. Yangqi stone cat eyes
The cat's eye is usually green, yellow-green, magnified and invisible to form the contents of the eyeliner. The eyeliner is diffused and inflexible. Under the light, it is a kind of "white-yellow-yellow" color (also known as "milk honey"). Phenomenon.) The measured refractive index is 1.62 or 1.63. The characteristic spectrum 505 nm absorption line is visible. Under the polarizer, the set of polarized light is often displayed.