09-28-2004, 06:16 AM
Join Date: May 2004
Location: Brooklyn, New York
iTrader Positive Rating: 100%
Judging by the use that Rex mentioned above and that it is capable of absorbing so much water, I would guess this substrate is based largely on clay minerals such as Montmorillonite otherwise classified as follows:
The Montmorillonite/Smectite Group |
This group is composed of several minerals including pyrophyllite, talc, vermiculite, sauconite, saponite, nontronite and montmorillonite They differ mostly in chemical content. The general formula is (Ca, Na, H)(Al, Mg, Fe, Zn)2(Si, Al)4O10(OH)2 - xH2O, where x represents the variable amount of water that members of this group could contain. Talc's formula, for example, is Mg3Si4O10(OH)2. The gibbsite layers of the kaolinite group can be replaced in this group by a similar layer that is analogous to the oxide brucite, (Mg2(OH)4). The structure of this group is composed of silicate layers sandwiching a gibbsite (or brucite) layer in between, in an s-g-s stacking sequence. The variable amounts of water molecules would lie between the s-g-s sandwiches.