Jarosewichite and a related phase: basic manganese arsenates of the chlorophoenicite group from Franklin, New Jersey

Jarosewichite, Mn3+Mn3+(AsOn)(OH)0, is a new mineral, closely related to chlorophoenicite, from the Franklin mine, Franklin, Sussex County, New Jersey, where it occurs associated with andradite, franklinite, flinkite, cahnite and hausmannite. Jarosewichite is orthorhombic, space grotp C2lmLlm2lm, C222 or Cmm2, with a : 6.56(3), b : 25.20(10), c : 10.00(5)4, and Z : 8. The strongest lines in the X-ray powder difraction pattern are (d, I, hkD 2.669 100 222,082;3.91 60 042, 061;1.788 50 (not indexed);2.503 0 242,261,004,0 l0 0. Jarosewichite is dark red, occurs in prismatic barrel-shaped aggregates, has a density o f 3 .66 (obs ) ,3 .70g l cm3(ca l c ) . I t i sb iax ia l ( )w i t h re f rac t i ve ind i cesd= 1 .780 (5 ) ,p= 1.795(5) and y= 1.805(5) ; theor ientat ionisX: a,Y: b,Z = c;p leochroismis weak,Z) X. Microprobe analysis with Mn3+ calculated, yields: FeO 0.4, MgO 2.l,CaO0.2,ZnO 1.2, MnO 42.3, Mn2O3 17.7 (IMn = 45.1 wt.%), AszOs 24.0, with H2O 12.1 percent by difference, sum : 100.0 percent. A second manganese arsenate from Franklin, New Jersey, is also related to chlorophoenicite, but may be heterogeneous. Although optical, chemical and crystallographic properties are characterized, there is sufficient ambiguity to deny it species status at this time. The data for this mineral, jarosewichite and chlorophoenicite imply the existence of a large family of related arsenates based on the structure principles outlined by Moore for chlorophoenicite.