Here's an attractive SKELETAL (FENSTER) QUARTZ crystal from Arramberri, Nueva Leon, Mexico. Skeletal quartz gets its name because when the crystal was formed, there was not enough material to completely fill in the matrix of the crystal, so open spaces were left inside the "skeleton" formed by the edges of the crystal. Fenster means window in German, and that's another term for this kind of growth. We found this fine crystal on the stand of one of the large wholesale dealers set up at the Tucson Gem, Rock & Mineral Show.

Like hoppered crystals, skeletal crystals have fully developed edges, but the inner spaces are hollow. The result is a step lattice formation, that looks like someone has taken out the insides of the crystals. Actually, these empty areas never filled in, because the crystal grew very rapidly and there either wasn't enough time or material to fill in the inside of the crystal. The interior edges, which are formed in the ussual quartz crystal form, look like a series of smaller and smaller steps going down to the center. The casue of the skeletal formation is that electrical attraction is stronger on the edges of the crystal, so they grow more rapidly than the centers.