|
USA | |
| [var. Carnelian] Dorothy M. Schlegal (1957) Gem Stones of the United States : USGS Bulletin 1042-G |
| [var. Agate] Eckel, Edwin Butt , Cobban, Robert R., Mosburg, Shirley K., Foord, Eugene E. (1997) Minerals of Colorado. Fulcrum Publishing. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| Eckel, Edwin Butt , Cobban, Robert R., Mosburg, Shirley K., Foord, Eugene E. (1997) Minerals of Colorado. Fulcrum Publishing. |
| Pearl, R.M. (1958) Colorado Gem Trails & Mineral Guide. Sage Books, Chicago, Illinois. |
| Landes, K.K. (1935) Colorado Pegmatites. American Mineralogist, 20(5), 319-333. |
| Luetcke, Rolf (n.d.) Personal communication. |
Crystal Park, El Paso County, Colorado, USA