Diggings in a 2 square mile tuffaceous ash flow that produce the "Mexican Coconut" geodes
Ref:
Cross, B. & Culp Zeitner J. (2006): Geodes Natures Treasures, P.11-41
Finkelman, R.B., H.T. Evans, and J.J. Matzko, (1974): Manganese minerals in geodes from Chihuahua, Mexico. Mineralogical Magazine, MARCH 1974, VOL. 39, PP. 549-58.
Hoffmann-Rothe, R. (2006): "Coconuts": Die Knack-Geoden von Las Choyas, Mexiko. LAPIS 31 (11), 47-50
Robert B. Finkelman, John J. Matzko, Ching Chang Woo, John Sampson White & Walter R. Brown (1972): A Scanning Electron Microscopy Study of Minerals in Geodes from Chihuahua, Mexico. Mineralogical Record 3:205-212.
