Tropidoleptus from the Silica Shale

Have I mentioned that Tropidoleptus carinatus is one of my favorite Brachiopods? I've shown specimens I've previously found in the Hungry Hollow Formation, the Moscow Formation and the Mahantango Formation. Today I'm showing off a specimen from the Silica formation that I purchased.

Pedicle valve

Front

Brachial Valve

Profile

I find it interesting to note the different ways the shell has been preserved. The variations are due to the minerals present when it was being permineralized (the process where minerals fill in the spaces left after the original shell material dissolves or is replaced). As I've only had a few opportunities to collect from the Silica Shale I have to supplement my collection with purchased specimens from time to time. Hopefully I will find one for myself in the future.