Quartz, originally uploaded by Shiny Things.

One bonus trip photo that I didn’t get to post earlier.

Petrified wood is actually a specialised form of quartz. Silica deposits from volcanic ash bild up in the wood, preserving its structure; the colours come from impurities. Red is iron; black is carbon; white is pure quartz. You also get blue shades from copper - and a ranger told me that they even get uranium-laced petrified wood.