MAGNETITE
Specimen mag-27
$ 36.00Dims: 4.52x2.32x1.65" (11.49x5.90x4.19cm)
Wt: 15.55oz (440g)
Potosi, Bolivia
This specimen displays perhaps a hundred magnetite crystals scattered over one surface of a pale host rock. The magnetite crystals are black and vitreous, as octahedrons. Oddly enough, many (perhaps most of the larger crystals) are cracked - I can think of nothing that might cause this other than a rapid temperature change. The host rock is a conglomerate consisting of a cream colored granular mineral, tiny magnetite crystals, and rounded distorted colorless crystals that I believe are quartz - one of them displays a conchoidal fracture. They may be a glass, of course, as this is likely a volcanic rock.