calcium carbonate rock...

[rossb]

**edited**

The rock I picked up is *($10)* $5.00 a kilogram . It is rather white but if you could visualize it with some crystaline algae on it (or in my case heavy diatom growth :shock: ) you would be hard pressed to tell the difference from real "live" rock. It has the added advantage/disadvantage of not carrying critters (nasty or nice) with it. It does not look at all mined and has interesting fossilized things of most of it.