AURICHALCITE
Specimen aur-3
$ 42.00Dims: 2.9" x 1.7" x 1.6"(7.4 x 4.3 x 4.1 cm)
Wt: 2.98 oz.(84.4 g)
Zacatecas, Mexico
Almost half of this specimen's surface area is covered by a crust made up of clusters of short, acicular needles of Aurichalcite. These needles are pale blue in coloration, have a dull luster, are translucent, and do not exceed 0.1"(3 mm) in length. Surprisingly, there is almost no visible damage to the crystals; the reason for this is that the crystals in the most exposed areas are covered with a crust of what I believe are intergrown calcite crystals. The calcite is mostly transparent, but is almost black in coloration. The documentation states that this is due to a layer of plattnerite, that coats the specimen as a thin dusting. If it does occur in crystals, they are far too small to effectively see even with a 10-power loupe; I think that at least 100x magnification or more is necessary. All of this rests on the inevitable limonite matrix that most Mexican minerals have. Some of the exposed Aurichalcite crystals have also been "dusted" with the plattnerite, making them a bit easier to define.