Abalone shells are sacred containers used to contain smoldering herbs & incense for smudging & ceremonies. To protect the bottom of the shell from high temperature you can add a layer of sand or bird gravel before burning sage leaves, sweetgrass, dried herbs, copal resin or palo santo wood.
Since they come in their natural form, each large shell is unique with individual colouring and markings. They vary in diameter but are approximately 6-7 inches in length.