An old term used for an object such as a crystal ball used for skrying. Perhaps the most famous belonged to John Dee and was used by his assistant, Edward Kelly, in their operations that resulted in the writing of the Enochian language and the birth of Enochian magick.

In the British Museum’s John Dee collection, there are two devices that he owned (although their validity has been questioned). The shewstone is an ovoid crystal with a metallic frame and short, attached chain, similar to a fob for a pocket watch. The other is a black obsidian mirror that has often been mistakenly called the shewstone. It may be that Dee referred to both of these and other reflective objects as shewstones.

In December of 2004, a man wearing a long black leather coat smashed the case holding the crystal, grabbed it, and ran down several flights of stairs to escape with the shewstone. It was recovered the following month.