Abraham's time for mercantile
transactions.

Gold is mentioned on the Egyptian monuments of the 4th dynasty, and
silver was probably of the same early time; but gold was evidently
known in Egypt before silver, which is consistent with reason, gold
being more easily obtained than silver, and frequently near the
surface or in streams.

The relative value and quantity of the precious metals in the earliest
times, in Egypt and Western Asia, are not known; and even if a greater
amount of gold were found mentioned in a tribute, this could be no
proof of the silver being more rare, as it might merely be intended to
show the richness of the gifts. In the tribute brought to Thothmes
III. by the Southern Ethiopians and three Asiatic people, the former
present scarcely any silver, but great quantities of gold in rings,
ingots, and dust. The Asiatic people of Pount bring two baskets of
gold rings, and one of gold dust in bags, a much smaller amount of
gold than the Ethiopians, and no silver; those of Kufa, or Kaf, more
silver than gold, and a considerable quantity of both made into vases
of handsome and varied shapes; and the Rot-[=n]-n (apparently living
on the Euphrates) present rather more gold than silver, a large basket
of gold and a smaller one of silver rings, two small silver and
several large gold vases, which are of the most elegant shape, as well
as colored glass or porcelain cups, and much incense and bitumen. The
great Asiatic tribute to the same king at Karnak, speaks in one place
of 100 ingots (or pounds weight?) of gold and silver, and afterwards
of 401 of silver; but the imperfect preservation of that record
prevents our ascertaining how much gold was brought, or the relative
proportions of the two metals.

M. Leon Faucher, indeed, suggested that the value of silver in some
countries originally equaled, if it did not exceed, that of gold ...
and the laws of Menes state that gold was worth two and a half times
more than silver.... Everywhere, except in India, between the fifth
and sixth century B.C., the relative value of gold and silver was 6 or
8 to 1, as it was in China and Japan at the end of the last century.
In Greece it was, according to Herodotus, as 13 to 1; afterwards, in
Plato's and Xenophon's time, and more than 100 years after the death
of Alexander, as 10 to 1, owing to the quantity of gold brought in
through the Persian war; when the value of both fell so much, that in
the time of Demosthenes it w