A dropstone of quartzite in layered rhythmite at Itu, Brazil. Dropstones are isolated fragments of rock found within finer-grained water-deposited sedimentary rocks or pyroclastic beds. They range in size from small pebbles to boulders.
The Dropa[1] stones are purported pseudoarcheological artifacts. They are claimed to be a series of 12,000-year old granite discs with inscribed markings that represent an account of an extraterrestrial crash landing on Earth.
1996年5月1日 · Dropstones are clasts which pose a hydrodynamic paradox or which have an exotic or extra-basinal lithology with uncertain provenance. Recently, dropstones have been consistently interpreted as...