If you are registered, you get access to the members only section, can participate in the buy & sell second hand forum and last but not least you can reserve your preferred username before someone else takes it.
The colors are a bit confusing. If you have a chance, could you take pictures of the stone while it's sitting on a piece of white paper? A shot more directly overhead might help too since the angle in the first picture might be causing glare (just a guess, I'm not a photographer). I want to say that it's a La Verte or a La Grise, but the dark lines on the side confuse me.