I meant the naturally occurring alloy, the one you dig up. I would
assume that it would quite rare. I've only seen one small piece in
an Egyptian exhibit
There are beautiful electrum pieces from the so-called “Royal
Cemetery” at Ur in ancient Mesopotamia (Iraq), ca. 2500 BC. They vary
in color because some were “enhanced” by chemically dissolving some
of the alloy in the surface layer (depletion gilding). See P.R.S.
Moorey, Ancient Mesopotamian Materials and Industries, pp. 216-240,
on precious metals, including a discussion of electrum.
Color photos of some of these ancient electrum artifacts may be seen
in the book edited by Zettler and Horne, Treasures from the Royal
Tombs of Ur, pp. 124, 133 (tumblers), p. 165 (electrum equid on top
of silver rein ring), p. 166 (electrum spearhead), p. 170 (electrum
shafthole adze), p. 171 (two chisels, perhaps of electrum), p. 173
(toilet set of silver and electrum). See pp. 125 and 163 for some
discussion on electrum.