Graphite from Berks County, Pennsylvania, USA
USA | |
| Rocks & Min.: 17:340. |
| The Mineralogy of Pennsylvania 1966-1975 Robert C. Smith II ( (quoted B. L. Miller 1912, p.114) (quoted B. L. Miller 1912, p.114) |
| Rocks & Min.: 15: 222. |
USA | |
| Rocks & Min.: 17:340. |
| The Mineralogy of Pennsylvania 1966-1975 Robert C. Smith II ( (quoted B. L. Miller 1912, p.114) (quoted B. L. Miller 1912, p.114) |
| Rocks & Min.: 15: 222. |