Further X-ray studies ensued; namely Wellin ( 1956 ) which determined the crystal structure of thaumasite, and Besjak & Jelenic ( 1966 ) which gave affirmation of the structure nature of ettringite.
12.
It occurs with calcite, ettringite, wollastonite, larnite, brownmillerite, gehlenite, diopside, pyrrhotite, grossular, spinel, afwillite, jennite, portlandite, jasmundite, melilite, kalsilite and corundum in the limestone xenoliths.
13.
Ettringite crystals have a P31c with a = 11.224 ? c = 21, 108 ? while thaumasite crystals fall into space group P6 3 with a = 11.04 ? c = 10.39 ?
14.
Ongoing research on ettringite and cement phase minerals is in general to find ways to immobilize wastes and heavy metals from soils and the environment; this can be done by use of the proper cement phase forming mineral by use of lattice to extract according elements.
15.
The mineral ettringite has a structure that runs parallel to the " c " axis-the needle axis-; in the middle of these two lie the sulfate ions and H 2 O molecules, the space group is " P31c ".
16.
An ettringite sample extracted from Scawt Hill was analysed by C . E . Tilley, the crystal was 1.1 x 0.8 0.5 mm, with specific gravity of 1.772?.002, the density was determined by immersing the sample in a solution of carbon tetrachloride mixed with bromoform.
17.
In the cement system, the presence of ettringite depends on the ratio of calcium sulfate to tri-calcium aluminate ( C3A ); when this ratio is low, ettringite forms during early hydration and then converts to the calcium aluminate monosulfate ( AFm phase or ( Al 2 O 3-Fe 2 O 3-mono ) ).
18.
In the cement system, the presence of ettringite depends on the ratio of calcium sulfate to tri-calcium aluminate ( C3A ); when this ratio is low, ettringite forms during early hydration and then converts to the calcium aluminate monosulfate ( AFm phase or ( Al 2 O 3-Fe 2 O 3-mono ) ).
19.
It is suggested that the crystal morphology of ettringite Ca 6 Al 2 ( SO 4 ) 3 ( OH ) 12 ?6H 2 O can incorporate a variety of divalent ions : Cu 2 +, Pb 2 +, Cd 2 + and Zn 2 +, which can substitute for the Ca 2 + by incorporating these ions into the lattice.
20.
Differences between structures of ettringite and thaumasite arise from the columns of cations and anions : Ettringite cation columns are composed of Ca 3 [ Al ( OH ) 6 ?2H 2 O ] 3 +, which run parallel to the " c " axis, and the other columns of sulfate anions and water molecules in channels parallel to these columns.
