Next time you are using a mortar and pestle, take a second to think about how long this device has been in use. It is found all over the world, and used by many cultures, including the ancient Chinese and the Aztecs. Some may even call this the first food processor. When you put spices, seeds and other foods in the mortar and grind with the pestle the oils, flavors and aromas that make up the foods are revealed. There are many types of mortars and pestles but the best quality are lava/basalt stones, because of their rough texture. This type of mortar and pestle will give you superior salsas, guacamole and mole sauces. You will also have a device that with just a little care will last many lifetimes.
Prepare or season your lava mortar and pestle for use. Run water onto the lava stone mortar and pestle. While running the water, scrub all surfaces with a stiff brush. Rinse, and let the stone air dry.
Drop a handful of uncooked white rice into the mortar. Use the pestle and grind the rice all over the bowl's interior. Throw away the ground up rice. Repeat this process until the ground up rice is white and not discolored.
Take the garlic, cumin, kosher salt, coarse black pepper and grind the mixture all over the interior of the mortar. Remove the mixture and throw it away when you are done grinding. Rinse the mortar and pestle thoroughly and allow them to air dry. This step completes the seasoning, and you only have to do these steps once before the first use.
Maintain your Lava stone mortar and pestle by simply rinsing it in warm water after each use.
According to Gourmet Sleuth there are fake lava stone mortars and pestles. They are made of concrete and crushed non-basalt river rock. This kind of mortar and pestle are very sandy or dusty and do not make a good grinding surface.
Do not use dish washing liquid or other cleaners on your Lava stone mortar and pestle. The stone could absorb the perfumes and soap and leave a funny taste in all food that you grind.