Quartz crystals, sometimes referred to as single-terminated or double-terminated crystal points, come in a variety of styles. You can get them undrilled or drilled. I like to get drilled crystals, because the hole provides a secure way to integrate them into your jewelry design.
I've used two different styles in my pendants, though there are many others out there.
The coated single-terminated crystals (seen in the gray pendants, above) are relatively small and have correspondingly small holes that work well with 24-gauge wire.
The double-terminated crystals (clear crystals, above) are larger, have 1 mm holes, and worked perfectly with 20-gauge wire.