Fragments of asteroids regularly land on Earth as meteorites. If you examine such a find, you can see that it comprises millimetre-sized round stones, known as chondrules. These small particles are ...

Kidney stones are small, hard deposits made of minerals and reoccurring materials inside the kidneys. Stones often go unnoticed in the kidney until they move into the ureter – the tube connecting the ...

Both gallstones and kidney stones can be very painful. Gallstones are deposits of digestive fluid, while kidney stones are crystals formed from chemicals in the urine. Both types of stones may pass.

Perfect circles of stones cover the ground in parts of Alaska and the Norwegian islands of Spitsbergen. Elsewhere in the far north, stones form other striking patterns on the ground: polygons, stripes ...