Dims: 3.5" x 2.4" x 1.7" (8.9 x 6.1 x 4.3 cm)
Wt: 6.28 oz
Morro Velho, Minas Gerais, Brazil
The Siderite crystals on this specimen occur in a trigonal, bladed form that is almost tabular in habit; they are actually flattened rhombohedrons. All have reasonably good definition, and damage is limited to only the most exposed crystals along the specimen's edges, including the largest crystal, whose dimensions measure 0.6 x 0.5 x 0.3" (1.5 x 1.3 x 0.8 cm). All of them have a dull brown coloration with a hint of green, and a dull, almost satiny luster. The green coloration and dull luster are due to a generous coating of tiny chlorite platelets that are dusted on the crystals. This also makes them only dimly translucent. There are a few other minerals present on the specimen that are worthy of mention, including several quartz crystals. These crystals have the standard hexagonal prismatic form that is common for them, though their edges are more rounded than usual, likely due to the chlorite that also heavily coats them. They have taken on the dull, deep green of the chlorite, and have a pearly, almost satiny luster of their own. They are also dimly translucent, though it is obvious from close examination that the chlorite does not pervade their interiors. There are also two patches of astonishingly clear, tabular apatite crystals! They are in the shape of flat, hexagonal tablets and are so heavily intergrown that their actual form is rather difficult to determine. They have well-defined edges and faces that reflect a bright, vitreous luster, and the crystals are transparent and remarkably clear, showing a few cloudy inclusions. Their color appears to be a very pale pink, but may actually be closer to colorless. If I didn't have the documentation, I would think that these platelets are actually beryls, as most of the apatites that I see don't have such definition. It is a very interesting and entertaining piece to examine.