100mm x 87mm
I love the extremely intricate fortification banding in this stone. This pseudomorph is both the largest and finest example I have found at St Cyrus to date. I have discovered others of even larger sizes that sadly have not displayed interiors even approaching the finesse of this stone. I am afraid that I cannot tell you at present, dear reader, which mineral might be the basis for the agate inclusions in this piece. However, I would nominate Calcite as the most likely culprit. It is interesting nonetheless to view tha larger crystal voids that have been filled with green chalcedony. I know that I have seen similar nodules of this mineral, without any agate content, so analysis to determine its identity would certainly be possible.
I picked up this agate in late April/May 2016. It was while the tide was on the ebb, and with a good wind behind me. A suggestion of fortification banding was visible on the outside, but there was no suggestion of the beauty that lay therein. Pseudomorphs (if indeed I am referring to these stones correctly) are an infrequent find at St Cyrus, but they DO occur, generally always in larger sizes than nodular agates and usually without striking markings. Similar material can also be found at Lunan Bay and at Usan.