A molcajete (mole-ka-HEE-tay) is an ancient meso-American tool used to grind spices and prepare salsas and guacamole. A true molcajete is made of volcanic rock and is used with a tejolote, much like a mortar and pestle. Because the volcanic material is very porous, the molcajete is never completely cleaned. Rather it seasons with use and imparts its own unique flavor over time.
Seasoning your molcajete
A new molcajete requires seasoning to smooth the interior and remove bits of loose rock. Seasoning is accomplished by grinding handfuls of rice into powder. The first few ground handfuls will turn gray as bits of rock flake off of the molcajete. Keep grinding new handfuls of rice until the rice powder is white. This process is not for the faint at heart. It is hard work, but can be stretched out over the course of a few days and hopefully a few volunteers. When you are ready to give up, keep going. When you are done you will have a tool for life, suitable to be passed down to your grandchildren. There are several good sources on the internet that describe variations in techniques for curing and seasoning a molcajete.
Cleaning your molcajete
To clean a molcajete NEVER use soap. Simply rinse with water and use a clean brush or a traditional escobetilla, a mexican pot scrubber made from the agave plant. (There are more good things made from the agave plant than just tequila!))
Buy the real McCoy
Molcajetes should be made of a single piece of dark volcanic rock. Avoid cheap cement imitations. A good molcajete will run between $25 and $50 depending on where you buy it and how large it is. Hint: bigger is better. You can purchase your molcajete online from a variety of vendors, including Amazon.