This particular brooch is a plaid or tartan pin that was used to secure the wearers clan tartan to their chest/shoulder area. The bloodstone in this brooch has beautiful red drops across the green of the stone. A gorgeous piece of white lace agate is also part of the border.
The stones on the arms of the cross form thistles. Knots separate the agates and add interest to the border. On the reverse you can see the layered construction with each arm of the cross attached to the base of the brooch. One of the agates has a chip. In the same area you can see that one of the agates has crazing but it is stable in the setting.
Both of these issues can be seen photo #9. Please look at all the photos so that you can judge condition. The brooch is in good antique condition with wear commensurate with age 153 years old!