Lost mines are a popular form of lost treasure legend. The mines involved usually contain a high-value commodity such as gold, silver or diamonds. Often, there is a map (sometimes called a "waybill") purportedly showing the location of the mine. Common reasons for the mines being lost include: Some lost mine legends have a historical basis; some have none. But the lure of lost mine legends is attested by the many books on the subject, and the popularity of publications such as Lost Treasure magazine.