The molcajete is essentially a mortar and pestle made from hand-carved volcanic stone. When buying one, it’s crucial to know if it’s legitimate and not a fake one made of cement.
Real molcajetes have pores that need to be cured to keep grit from the pores from mixing with food. Plus, when flavors get into the pores, they stay there, enhancing future dishes.
Working with volcanic stone can be difficult, especially for artisans who carve them by hand using only a hammer and chisel, so real molcajetes aren't always perfectly symmetrical.
However, cement-laden fakes are typically made from molds, so they always look perfect. They also lack visible pores (despite cement being porous) and thus look way too smooth.
The grit is another indicator that volcanic stone was used in construction. To test if a molcajete is real, pour a little water on its bottom, and leave it there for a few minutes.
Real molcajetes can leak if they have too many pores, but some water should remain in the bowl after a few minutes. However, fake ones usually absorb the water almost immediately.
If you’ve already bought a molcajete, scratching it with a knife will leave a permanent mark if it’s fake. That won't happen if the tool is real, but it may produce a little dust.
Cement molcajetes shouldn’t be used, at least for food purposes, as concrete ingredients like sand and gravel can end up in your food, so it’s best to return them and get a refund.