Well the big 'un was hit with a BFH :) and split almost perfectly across the face.
I'm a novice prepper. I used a dremel with a variety of bits to etch away the matrix (An air pen would no doubt have been much faster). And now I'm using, water, a touthbrush, a magnifying glass and one of those dentist type metal pointy thingies (bought from hobbycraft).
Wetting the fossils darkens the matrix, which when scratched shows white. Makes it easier to work out what to pick at and what not to pick at.
I've asked the wife for a compressor/air pen/air abrassion set up from my birthday :)