Nodule in Limestone

["John VanCamp" <jvcstnwrks@xxxxxxxxxxxxx>]

Hi Tony.   I am not at all familiar with the Portland stone,
nor any of the other limestones from your part of the world.
However, I have had the opportunity to work with many
limestone varieties from here in Texas, and I can tell you
 from experience that it is not uncommon to find nodules such
as you describe, among other things. Some formations tend to
the iron sulfides while others tend towards the flint
deposits, depending on their post depositional history.  And
since limestone is a sedimentary deposit, any thing that
finds its way to the bottom of the sea during deposition is
included in the stone if it is capable of being fossilized.
Shells, bone, wood on occasion, I have even found a piece of
quartzite gravel that from its appearance, I believe to be a
gastrolith left behind by some long forgotten Cretaceous
creature.

Currently, we are seeing more and more of a secondary
mineral deposit in our primary carving stone (Cordova
Crème).  Local carvers call it flint, but it is not
concentrated in dense nodules like a normal flint deposit,
but rather a substance that fills the minute spaces between
the calcium carbonate grains, creating extremely hard spots
in an otherwise delightful carving material. Needless to
say, it gives us fits when trying to hand carve an
architectural element, as it tends to stand proud of the
finished surface, making a good clean line virtually
impossible. Hopefully, the quarry will get back into the
"GOOD STUFF" one of these days. Ah but I digress. Good luck
with you carving, and I do hope that you were able to work
around your inclusion so that it had no effect on the
finished piece.  John VanCamp