Sillimanite from Delaware County, Pennsylvania, USA
USA | |
| www.libraries.psu.edu/emsl/guides/X/delaware.htm. |
| Mineralogy of Pennsylvania-1922 Samuel S. Gordon, pg. 185 |
| Gordon, 1922. Mineralogy of Pennsylvania |
| Gordon, "Mineralogy of Pennsylvania," 1922 p. 195. |
Morton Homestead, Prospect Park, Ridley Township, Delaware County, Pennsylvania, USA