Yes, the stone is agate. I researched it:
It is one of the oldest stones and is said to attract strength and ward off storms. It is supposed to be good for the gums and for curing stomach upsets. Apparently everyone should carry one of these for protection.
Well, this stone did not protect my hands one bit as I tatted the edging. My fingers are a mess - very sore from tightening the silk around the pearl beads.
Tatting over metal this big - (over 3 3/4 inches long) is not easy because I had to accommodate that immovable bar. The Zwicky silk I used did not add to the ease of the process, but it was the perfect colour. Figures. I have a box full of different colours and that one little spool of silk was the ONLY colour that worked with the pendant.
The pendant - picked up, again be chance - in a store I never frequent, but thought I'd have a look, just in case.
I have turned into a regular Tatting Sherlock, it seems, lurking around old shops, yard sales, antique shops and anything that looks remotely interesting as far as unusual or vintage jewellery is concerned, prowling for a bargain and a unique piece of something or other!
This photo is not the best as I noticed the stitches need to be straightened - but I could not wait till I had taken another pic to post it.
Interesting thing about this agate is that it changes colour according to the light - sometimes it looks green and in brighter light the blue is more prominent.