Rick,
According to Susan Feniger and Mary Sue Siegal in their
Mexican Food For Dummies http://www.dummies.com/WileyCDA/Dumm...764551698.html, a molcajete is a black grinding stone made of basalt used to grind spices and guacamole.
Though the molcajete that is made from basalt may be limited to grinding those softer ingredients, apparently there are molcajetes
http://www.gourmetsleuth.com/mortarp...ere%20to%20buy made of stronger materials that can be used to grind foods as tough as corn.
Traditionally, though, the metate
http://www.public.iastate.edu/~rjsal...mages/azwo.gif http://www.public.iastate.edu/~rjsal...images/pat.gif has been used by many mesoamerican cultures like the Aztecs and the Mayas to grind corn but they first softened the kernels overnight with lime or ashes to make nixtamal or what we might call hominy and then grouund up the softened maize on the metate to make masa that was and still is used to make tortillas, sopes, chalupes, gorditas, picadas, taquitos (tacos), and tamales to name a few.
Metate grinding stones are hard to find in Boston, so I suggest if you want one soon, you shop for it on the Internet.
If you don't care what materials are involved in the grinding of your corn, you can get a variety of grinders including: metal grinding mills, mills that have caborundum stones, and mills that are made from granite or other tough stones.
The Corona Grain Mill
http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW usually comes with metal plates but you can attach a couple of carborundum stones to get a cooler ground grain.
There are a great variety of manual and electric grain mills out there and for starters I suggest checking out this site:
http://www.discountnaturalfoods.com/shopnew/mills.html.
I've owned both a manual stone mill
http://www.miracleexclusives.com/Sam...tone_Mill.html and an electric stone mill
http://www.miracleexclusives.com/Sam...tone_Mill.html and I feel that they are great investments if you can afford them.
The choices are yours.
Muchos gracias,
Bruce Paine