How should vermiculite concrete look once it is cured?

[RTflorida]

VV, for what its worth - coming from a fellow serf I agree with Jim and Maver, you should be fine. I followed the directions to the letter and you description of the end result sounds like what I had/have. No, it doesn't set up hard and rigid like concrete - yes, I can dig it out with a screwdriver, and yes - it will compress under too much pressure. I actually (foolishly) put a "dent" in the area surrounding my dome by kneeling on the hearth slab while cleaning the inside of the dome during construction. I am not at all concerned, other than my kneeling and rubbing a bit of the edges off while constructing, I've had no issues.
Because of the silicone issue, you might want to give it an extra couple of days of cure time, just to be safe. It does seem to get harder (and compress less) over time. Mine is 5 weeks old, was standing and kneeling on it again during the insulation process this past weekend......no "dents" this time around - but a screwdriver could still do serious damage.
Good luck and keep us posted

RT