Dims: 1.3 x 1.3 x 0.5" (3.3 x 3.3 x 1.3 cm)
Wt: 9.2 g
Malacacheta, Minas Gerais, Brazil
This lovely specimen consists of at least 5 "books" of tabular Autunite crystals that are held together through intergrowth with themselves and a few small tabular albite crystals. The Autunite books are generally in excellent condition, showing only a small amount of human-induced damage. Their tetragonal tabular form is excellent, with sharp edges and smooth faces that possess a pearly luster. Needless to say, they have the bright yellow coloration that is a primary characteristic of this mineral and are only dimly translucent even under halogen light. There is a substantial amount of a rust-colored, powdery material scattered about on the piece, but most of this appears to be a decomposition residue from what may have been the base rock. The albites are of the tabular variety known as cleavelandite and are in good condition. They show the standard pseudohexagonal tabular form and are colorless, transparent, and mostly clear.