- Cabinet, 10.5 x 8.2 x 4.8 cm
- Pomeroy Mine, Georgetown District (Southern Cross District; Cable District), Deer Lodge Co., Montana, USA
Another relatively unknown mineral, ludwigite (Mg2Fe3+BO5) typically forms in magnesian iron skarns and contact metamorphic deposits. It forms a series with vonsenite. In this large and rich specimen from the Pomeroy iron mine in Montana, it has formed bright black, radial fibrous aggregates. Old material and a rare Montana piece of some note. Ex. Elling Collection.