The real story
In Indonesia, the classic mortar (cobek) and pestle (ulekan) are cut from andesite, a volcanic stone. Around Muntilan, on the slopes of Mount Merapi in Central Java, whole villages of carvers chisel them by hand from lava rock the volcano keeps delivering.
The rough, porous stone is the point: it tears chili and shallot cells open instead of slicing them, which is why many cooks swear stone-ground sambal tastes brighter than blender sambal. A new cobek is often 'seasoned' by grinding rice or sand first to wear off loose grit, and a well-used one gets smoother and darker with every year in the kitchen.
