Sorry to rain on anyone's parade but I was considering taking this and spoke to a biochemist friend about it. She was horrified and emailed me this link:

http://www.vitalhealthzone.com/nutri.../silica.html#9

Note it says over 100mg a day is toxic. The tolerable upper limit is 29-30mg and that should come from food anyway. It is very rare to be deficient in it.
Please note it says toxic levels can cause irreversible kidney damage.
It also says you must consult a doctor if you are considering taking any silica supplement.
I know how tempting it is to take these things to speed up hair growth but please don't take this stuff, or at least do so in full awareness of the risks.
With love,
Toadstool xxxx