Thursday, January 31, 2013

The Earth As Canvas

Lovely designs on a page of sandstone in the desert. No, not petroglyphs or any design from the hand of humankind, but the art of the earth itself.

Some time ago, I wrote a post on Liesegang bands, circular rings of color deposited on a rock by the chemical diffusion of metallic elements in ground waters. This sandstone from the Nevadan desert illustrates this process – the colors show the wandering of various kinds of cations of iron (red to yellow), manganese (purple-blue to black), zinc (white to blue; near maroon when deposited as sphalerite), green (copper) and yellow (barium generally yellow in these circumstances). The white crusty deposits on this sandstone look very much like the kind of crusty carbonates mixed with clays that are associated with hydrothermal (hot spring) systems.

In addition to just being a lovely but superfluous addition onto the rock, these colors show the mineral explorationist a view of what is (or was) carried in the hydrothermal system: cooler waters carry the more mobile elements like manganese and can include deposits of gold and silver; warmer waters carry the less mobile zinc and copper. A lovely rock surface like this one is like part of a halo of fluids surrounding the core of a hydrothermal mineral deposit.

All the colors on the rock of this photo essentially shout to the geologist that somewhere nearby is a deposit of sulphide minerals, and thus could lead to a discovery of copper, silver, or even gold. How near? Where? Feel a sudden urge to do a bit of exploring?

With such lovely indications as this, mineral exploration and art exploration can go hand in hand. The Earth – we love it for the science, we love the science because it can be so damned beautiful!

Photo used with thanks by Doyle Wayman from his Facebook page 321go explore.

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