In the
tectosilicate structure of quartz, in which there is no center of symmetry, enantiomorphism results from how the tetrahedral Si[O.sub.4] polyhedra connect, at their points, to form helical chains, which, like spiral staircases, turn either clockwise or counterclockwise.
When you enter it, the database automatically completes the name, enters the mineral group (such as feldspars), if any, the crystal system, the chemical class (such as
tectosilicate), and the chemistry (K aluminosilicate).
Green River Westerly Mineral group shale granite Carbonates (%) 51.8 0
Tectosilicates (%) 45.9 5 Phyllosilicates (%) 2.3 95 Reference [21] [34] Green River Westerly Mechanical property shale granite Young's modulus (GPa) 3.2-3.8 76 Poisson ratio 0.345-0.365 0.27 Reference [35] [36]
In the past, zeolites were limited to
tectosilicates and tetrahedrons containing aluminum and silicon.
In one way the organization here is conventional, the chapters moving in Dana order from native elements through
tectosilicates, to end at last with opal, a non-crystalline "mineraloid." But there is much more history along the way.
Nitric acid-extractable K represents exchangeable K plus some K extracted from within phyllosilicate and
tectosilicates mineral structures.
These data are consistent with a dissolution-precipitation process in
tectosilicates, but it is very similar to that of the montmorillonite transformation.
The minerals ranged into groups I (micas) and II (
tectosilicates) contain alkaline metals strongly bonded in the mineral structure while in minerals ranged into groups III (smectites) and IV (zeolites) the alkaline metals are weakly bonded in the interlayer and in the structure channels, respectively.