Laubmannite is a combination of several rare phosphate minerals: Kidwellite, Dufrenite, and Beraunite. Each is a different phosphate phase of similar compositions producing concentric color zones. This is a real nice specimen.
Laubmannite
Formula
Fe++3Fe+++6(PO4)4(OH)12
Crystal System
Orthorhombic
Luster
Vitreous - Silky
Color
brown, greenish brown, grayish green, yellow green, dark green