Dims: 4.3 x 4.2 x 2.3" (10.9 x 10.7 x 5.8 cm)
Wt: 2 lbs., 7.1 oz. (1.108 kg)
Morro Velho, Minas Gerais, Brazil
This large hand specimen consists of a cluster of both Siderite and either ankerite or calcite blades (most likely ankerite). Though many of the Siderites are damaged, they are of larger size than the ankerites, having diameters of up to 0.9" (2.3 cm). Their trigonal tabular form is good; though "termination" edges are very rounded and difficult to define, their outer edges are very sharp. All have faces that are heavily patterned and graded, slightly dimming their high pearly luster. Though the ankerite crystals are very similar in form and luster, the two are easy to tell apart- the larger Siderites have a moderately pale brown coloration, whereas the ankerites are milky-white. Both show dim transparence. The ankerites are lightly dusted with small hexagonal platelets of a sulfide mineral, which I believe is marcasite or pyrrhotite. The Siderite/ankerite crust covers most of the surface of the gray calcareous host rock.