Black tourmaline and smoky quartz on albite matrix with hyalite Rhyolite These arches are made by

These arches are made by drilling a hole through a chunk of sandstone and sandblasting the material into a smoothed arch

This material would most accurately be named "chrysanthemum rhyolite" but you know I can't pass up a goblin-y name like spider jasper

and a grotesque off-brown version on the other side

There are a few patches of broken crystals on the surface

Black tourmaline and smoky quartz on albite matrix with hyalite Rhyolite These arches are made byLocale: Erongo Mountain, Namibia Approx dimensions: 4. 5 x 4 x 1. 5" Approx weight: 728g (1. 6 lbs) This large specimen is one of my favorites of the Erongo black tourmaline, known as schorl. The piece is a rough aggregate of minerals appearing to contain albite, schorl, and smoky quartz. The front is nearly entirely covered with dozens of blocky small schorl crystals, some displaying the Mercedes termination characteristic of the Erongo region.