Today I put some tests on my cretean purchases from last September to evaluate their potential of being subject to fusion imaging. I bought three Nautilus shells and two sea snails, holding them in the store against the sun to check their transparency. My untidy studio accommodated these precious stones under quite a bunch of something.
The best representation is with a black background, i.e. with inverted L-channel in Lab colors. With a black background a soft shining light appears in the objects.
This snail has a shape a triangle and resembles a bear claw or an Apollo capsule in the late Sixties. The translucency is very little.