Something I hate nowadays is when you buy a fresh packet of basmati rice from the local grocery store, expecting some outstanding quality that is seriously going to set off your taste buds in your mouth, only to be disappointed when you receive stoned filled rice packets, with this odd taste of pasty limestone.
Walmart is notoriously bad at this and I believe it has to be a quality control issue of them not checking their rice properly, hopefully they improve as we verge further into 2017 and with more and more customers looking to complain about the rice quality we can only expect better things to come from our local Walmarts.
When dissecting the stones that seem to be mixed into the rice we found that they were mainly composed of limestone. Occasionally there were traces of Iron, Lithium and Magnesium inside the rice, however the majority seems to be made from a limestone base, we account the limestone fragments in the bag down to the plants being next to a quarry or other type of construction area. When these two are close together the water feeding the rice plants can sometimes mix with nearby construction work and create stones inside the rice harvest.
The most annoying thing is to place the rice with the stones inside a rice cooker, we heard many stories from our friends at ricecookerworld of how the stones became insanely hot and would burn holes through plastic in the machine, and cause issues when it comes to cooking of the food. To avoid this either go for some high quality rice to avoid the stones or manually filter out the stones with your hands. A sieve may work however finding the right dimensions of the holes to allow the rice through but not the stones can be tricky so this may be best to avoid.