[Chemical composition] often contains similar substances such as Fe, Mn, Mg, etc.; when a certain amount is reached, iron wollastonite , manganese wollastonite and other variants can be formed.
[Crystal structure] three oblique system; 
a 0 = 0.794 nm, b 0 = 0.732 nm, c 0 = 0.707 nm; α = 90 ° 18',  β = 95 ° 24', γ = 103 ° 24'; Z = 2. The crystal structure of wollastonite (Fig. G-32) is characterized by [Si 3 O 9 ] single with three [SiO 4 ] tetrahedrons as a repeating unit (which can be regarded as an isolated tetrahedron and a double tetrahedron). The chain extends parallel to the b-axis (one of the tetrahedral ribs is parallel to the direction in which the chain extends), and the chains are arranged in parallel with the chain; the inter-chain gap is filled only by Ca to form a [CaO 6 ] octahedron. [CaO 6 ] octahedral co-edges are joined into a chain parallel to the b-axis, where the length of two co-angular [CaO 6 ] octahedrons is exactly equal to the repeating unit of the tetrahedral chain (about 0.72 nm), also with the unit cell The parameter b 0 values ​​are roughly equivalent.
Figure G-32 Crystal structure of wollastonite (cited from Pan Zhaoyu et al., 1993)
[Formation] Crystals often have plate-like crystals elongated along the b-axis (so formerly known as slate). Double crystal
(100) or (001) is formed. It is a sheet, radial or fibrous aggregate (Fig. G-33).
Figure G-33 Crystal morphology of wollastonite
[Physical properties] White or gray with light gray and light red, a few are meat red; glass luster, cleavage surface sometimes presents pearl luster. The cleave {100} is complete, {001}, {102} medium, (100) ∧ (001) = 74°. Hardness 4.5 to 5.5. The relative density is 2.75 to 3.10. It is known that wollastonite containing 0.02% to 0.1% of Mn emits strong yellow cathode light fluorescence. The temperature of 1540 ° C.
[genesis and occurrence] is a typical metamorphic mineral, often appearing in the contact zone between acidic magmatic rock and carbonate rock, which is the product of high temperature reaction. Reaction formula: 3CaCO 3 +3SiO 2 —→Ca 3 [Si 3 O 9 ]+3CO 2 Synthesis experiments show that the reaction proceeds from left to right under constant pressure or constant temperature and pressure reduction; under constant temperature and pressure conditions The reaction proceeds from right to left. In addition, wollastonite is also found in deep metamorphic calcareous chip rocks, some alkaline rocks of volcanic eruptions.
[identification characteristics] morphology, color, symbiotic minerals. The difference from tremolite is that the wollastonite is softer, not like the tremolite brittle and easy to fold; the difference from the sillimanite is that the form is different and soluble in acid.
[Main use] Many valuable and unique properties of wollastonite are mainly derived from its needle-like and fibrous form, such as "stone wool"; added to the ceramic charge, after partial melting, unmelted wollastonite The needle-shaped body forms a dense grid, so that its original volume is not easy to change. During the condensation process, the crystallization of the charge causes the wollastonite needle-like bodies to be tightly fastened together, thus maintaining the blank size and being difficult to maintain. Fragmentation. In addition, the produced semi-molten porcelain has the advantages of low porcelainization temperature, increased strength, reduced shrinkage, and water swelling. With the need for phosphors defense industry, it has been begun to use CaSiO 3 · Mn phosphor may be replaced ZnBe [SiO 4] phosphor.
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