- Montgomeryite, Jahnsite
- Cabinet, 11.1 x 6.9 x 5.3 cm
- Tip Top Mine (Tip Top pegmatite), Fourmile, Custer District, Custer Co., South Dakota, USA
Montgomeryite and Jahnsite are rare phosphates and the Tip Top Quarry is the Type Locality for jahnsite. Lustrous, orange Montgomeryite crystals and contrasting, black Jahnsite and rockbridgeite richly cover the partially euhedral cabinet sized orthoclase crystal on this fine specimen. There may be mitridatite as well. Highly representative, very rich and a large specimen with these rare phosphates from this well-known locale. Collected in the 1980s.