Carborundum Stone

"This was used by my husbands descendants on their farm for knife sharpening. It is well worn so it obviously did its job. The stone was discovered by Edward G Addison in 1920 and is the second hardest substance known to man. It is rare but is still used today in manufacturing sharpening aids, Military Vests and even the Nuclear Industry. This item is just of great sentimemental value to my husband."