The Tourmaline nuggets shown in the large photo are rough-cut stones separated by small round lava stone beads. Perfect for a casual masculine bracelet. 
The beads are strung on heavy beading wire and fastened with a fold-over clasp. Wear it with any of the other stackers shown.
They can be worn loose fit or snug. When you measure (see Design It for sizing info) make sure you measure your wrist where you want the bracelet to rest.