Yes, it is a fossilized algae, a natural silica mineral.
They say that we have already been eating it but in small amounts. It is sometimes mixed with grain to kill bugs. Surely the way the FDA is against natural health products they would jump on the necks of those that sell this to be consumed. In other words, they search for ways to get these things banned and controlled. I'm thinking that if they had a leg to stand on this would have been outlawed half a century ago. I am reading a book written on this by an RN named Tui Rose. It is entitled Going Green Using Diatomaceous earth.