This is a natural Blue Apatite Pendant with a drilled hole in a tear shape. You can team them up with bracelets. Here is a video of one of the group.
This crystal is known for its positive use of personal power to achieve goals. It clears away confusion, apathy or negativity. And then stimulates the intellect which expands knowledge and truth. It is said to encourage the formation of new cells and aids in the absorption of calcium. It helps heal bones and teeth while it also repairs cartilage.
Take this blue apatite pendant to a jeweler and get a silver or gold jump ring added to thread you chains on. Or, find a thin string for a casual look. Could also go in a hemp necklace. And you can buy a bail loop to class it up.
Note some have “nicks” at back that weren’t full polished out. This won’t affect getting them set or their energy.
Dimensions are for the “B” blue apatite pendant, but if you need exact dimensions ask.