Geology - Weathering

Harder calcite (I think) veins weathering out of Aztec Sandstone. Valley of Fire State Park, Nevada, USA. The Aztec is correlative with the Navajo Sandstone of Utah and northern Arizona, but for historical reasons has a different name here. The calcite crystallized in cracks. You can tell this is a desert area, because the _calcite_ would weather first if the climate weren't so arid!

Precipitation from solution fronts, a natural analog of chromatography. The red mineral is hematite (ferric oxide), with some orange goethite (iron oxyhydroxide, better known as rust). This sort of weathering is very common in arid environments. Aztec Sandstone, southern Nevada, USA. The coin is there to show scale and is about 1 inch (2.5 cm) across.

Above Virginia Lakes trail.