As a form of Quartz, yes.. moreover it appears to be a section of a geode thou the color seems a bit off.. I would say that it might have faded or could be a smokey quartz geode section. Is it possible to explain or show better what colors are within this sample?
Try taking a pic or two with the rock sitting on a white table cloth or white cloth. The red table cloth tends to askew the true colors in the rock because of the reflection coming from it!
A massive formation of quartz. What I generically call rock crystal. The individual crystals have formed into each other creating a solid piece that's whats called a massive form. Had there been a vug, an empty cavity, in conjunction with the crystal formation you would be able to see individual crystal points. You can sometimes get some gemmy stuff out of rock crystal but more often there is a lot of internal fracturing. The internal fractures and contact areas between the crystals make for very nice plays of light and appear luminous