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Message:: [QUOTE="Rob Woodside, post: 3178444, member: 96187"]A well focused electron beam should leave a micron sized blemish that's not eye visible. I presume, but don't know of any literature on this, but I suspect there's a small industry looking at the impurities and identifying sources. Native gold usually has silver has the major contaminant, anything from a few to 40% or more by weight. The more silver, the paler it is. More than 20% Silver is often called electrum. Some localities produce a browner gold with  a few % palladium. I don't know if Tellurium survives the smelting or just goes up the smoke stack. A few % copper reddens it. Rough gold is quite variable but Ontario rough gold ought to be around 85% gold. As there is a hydrologic cycle, so there is a gold cycle. Very rarely the gold deposits in open spaces or in mud and forms crystals, mostly the gold just fills the veins with no crystals evident. The state of crystallization depends on the space available and not on the impurities, though they can influence the the habit (coarse, dendritic, etc.). These deposits weather away and the gold is rolled into ever smaller nuggets. Eventually they are tiny particles in black sand at the sea shore. THis fine gold is then washed out to sea and gets caught on a subducting plate. A few hundred kilometers below the subducting plate is digested and the dispersed gold is concentrated and then deposited in the veins where it might crystallize.[/QUOTE]