"Quartz is non-porous, making it resistant to stains and bacteria," he explains. Some types of stone, such as marble, are porous, which means that dirt, liquid, and bacteria can seep in.

There are several types of kidney stones and causes for them. While some stones stay in the kidneys and go undetected, others leave and have the potential to cause significant pain and, in some cases, ...

Bone fish hooks were ground until sharp on a stone like this. What do you think needles and fish hooks were made of after the Europeans arrived? Can you think why the people would adopt the new ...