A close up of one of the chunks of obsidian in yesterday's photo, the one near the doorknob on the right. It's not easy to see at this scale, but there's a bit of a glow to the red portion in that lower squiggle. Rock hounds have a slew of names for various colors and textures in what geologists would consider to be a single rock or mineral type. Plain red obsidian is called "mahogany," but examples like this, which preferentially reflect light at certain angles, are called "fire mahogany." Indeed, the dancing play of light can be quite reminiscent of flames in the right samples in the right conditions. It's quite lovely. I suspect the effect is due to an alignment of microscopic crystals- possibly hematite or magnetite- caused during viscous flow. It's fairly common, as I mentioned yesterday, at Glass Butte, about an hour east of Bend.