A regular dodecahedron can be formed from a cube in the following way: The top square in the cube is replaced by a "roof" composed of two pentagons, joined along the top of the roof. The diagonals in the pentagons parallel to the top of the roof coincide with two opposite sides of the square. The other five squares are replaced by a pair of pentagons in a similar way. The pyritohedron is constructed by changing the slope of these "roofs".
Pseudomorphs from Peru: pseudomorphs, crystals that have been replaced by another species while retaining their original shape, have been found in remarkable variety in the mines and mineral deposits of Peru. They provide evidence of changing chemical and physical conditions within ore deposits, and also make fascinating specimens.(Report)
Mar 01, 2008; INTRODUCTION Pseudomorphs (replaced crystals) and perimorphs (molds of dissolved crystals) are a rare but very interesting part...