Post by Admin on Feb 4, 2023 7:27:42 GMT -7
"Simple SiO2" is AMA-ZING-LY complicated! Especially with water.
Water is held together by weak hydrogen or pi bonds, easily breaks apart - "ionizes," while Quartz is held together by strong multiple lattice covalent bonds.
Very Low (acid) and Very High (base) pH will eat the flesh off your bones.
Acid will dissolve calcite and similar elements, but base will force them to be deposited.
On the other hand, Base will dissolve a little silica, while acid forces silica to be deposited.
Even in very high pH, SiO2 is not very soluble.
Acid will dissolve calcite and similar elements, but base will force them to be deposited.
On the other hand, Base will dissolve a little silica, while acid forces silica to be deposited.
Even in very high pH, SiO2 is not very soluble.
Why low solubility? Because silicon atoms are larger than carbon atoms, silicon-oxygen bonds are longer than C02 carbon-oxygen equivalents. The p orbitals on silicon and oxygen cannot overlap enough to form weak pi bonds. Therefore, only single strong covalent bonds are formed. So each silicon atom forms four single covalent bonds with four oxygen atoms, and each oxygen atom forms two single covalent bonds with two silicon atoms.
With each of the silicon atoms bridged to its four neighbors via an oxygen atom also attached to the neighbor silicon atoms, this forms a large network covalent structure. Strong bonds in three dimensions make silicon dioxide a hard, high melting point solid with a structure similar to that of diamonds. The bond energy is estimated at 621.7 kJ/mol.
To top it off, MOST SUBSTANCES ARE HYDROPHILIC (water loving), while SiO2 in most forms is HYDROPHOBIC! That is, they have H- or OH- negative surfaces that repel negative H2O.
Where do those occasional huge amounts of silica in solution come from?
That answer came from JOHN ELLISTON in Australia!
Shock waves shatter rocks - AND SILICA BONDS! Ground water ionizes, grabs those newly freed Si bonds, become rivers of Si-H or Si-OH fibers and start filling in voids. Agate is made.
There you have it. Most Agate layers were formed back when earth had it’s worst shocks, the dying times!
Agate is periodically a sedimentary rock !
NOTE:
Normally in different high pH locations Alkaline and Alkaline Earth elements are deposited and replaced in the groundwater with only minor amounts of silica.
Much of New Agate is held together by weak hydrogen bonds! As the agate dries the water evaporates and the hydrogen bonds are replaced as Si and O make new strong connections!
This is why the heat treatment hardens flint for napping.
