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Photographer's Note

Petra is one of the world's most beautiful architectural sites carved from some of the oldest exposed sandstone on Earth (Cambrian and Ordovician sanstone that is 450-550 million years old). However, the sandstone in Petra is typical in that it is comprised of colorless quartz clasts (the particles in sandstone) attached by a matrix binding that is composed of silica (Si), calcium (Ca), iron (Fe), aluminum (Al), manganese (Mn) and minor amounts of others (sodium (Na), lithium (Li), etc.). So the colors are only a function of colorants present in the matrix: browns from iron, yellows from Na and Fe, pinks from Na and Li, etc.

These minor matrix elements (ie. Ca, Mg, Mn, Fe, etc.) have mobilized and separated into what is commonly called 'Liesegang Banding' (banding in color and composition of ores caused by diffusion). However, the banding has been erroneously (and commonly) attributed to its deposition, but in fact when examined (and often simply observed) the original bedding (from coastal fluvial and dunal deposition) is unrelated to these spectacular colors that are not to be seen in the same way anywhere else on Earth.

In fact the colors are covered by a sort of 'drapery' given by recent and secondary deposition of simple calcium carbonates that are relased from the matrix and then redeposited atop and below the sandstone. This drapery is not very durable and is easily broken-off or eroded.
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Additional Photos by Yiannis Logiotatidis (logios) Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 179 W: 28 N: 398] (1903)
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