You are looking at a bloodstone skull buckle.

The martyr stone aptly named, due to the legend of this stone being at the foot of the cross and stained by the drops of blood from Jesus. Metaphysically, bloodstone is used to either promote a calm, tranquil atmosphere that is grounding or revitalize insufficient energy. A great stone for mental exhaustion. This stone represents both courage and strength and is used for achieving these attributes. It is associated with honesty and integrity and is useful in removing obstacles in life. A classic stone for wealth, it attracts abundance and good luck. Most effective on the Heart (green) and Root (red) Chakra.