Tejolote is the Aztec term for a pestle used with a stone grinder (molcajete). Typically this type of grinder would be used soft foods such for chiles, herbs, salsas. These pestles may be cone shaped, like the one shown above; or another typical version has an hourglass shape (shown below).
Usually your molcajete will come with a pestle. If you need to replace a pestle you can buy them online at GourmetSleuth.com
You should wash the pestle well before using. Use hot soapy water (don't used perfumed soaps which will absorb into the stone). Scrub the stone with a stiff-bristled brush. Allow the stone to air dry OR it can go into an oven at 350F until dry. This will sterilize the stone at the same time.
Pestles can go in the dishwasher; just make sure they can't come in contact with any fragile items.