|
USA | |
| Gleba, Peter P. (2008) Massachusetts Mineral and Fossil Localities. Kreueger Enterprises, Inc. |
| P Cristofono collection , 2009 |
| Eckert (1987): Earth Treasures Vol.1: The Northeastern Quadrant. Sears, John Henry (1905): The Physical Geography, Geology, Mineralogy and Paleontology of Essex County, Massachusetts |
| Morrill, P. (1960) New Hampshire Mines and Mineral Localities, 2nd edition. Dartmouth College Museum, Hanover, New Hampshire, 46 pages. |
Blackburn Circle locality, Gloucester, Essex County, Massachusetts, USA