Obsidian is one of the few stones that can be carved to a genuinely sharp edge, because it has no internal crystal structure to fracture along. That property is why it was used for cutting tools before metals, and it is the reason the detail on a small obsidian carving stays legible where a softer stone would blur.
The trade-off is fragility at thin points — a claw or an ear can chip if the pendant knocks against something hard. Handle it by the bail rather than the carving.
The Pixiu itself is a folklore figure rather than a religious one: a creature of appetite, depicted with a full belly and a sealed rear, and worn as an emblem of holding on to what you have earned. We describe the story because it is the reason the carving exists.