Byzantine silver is
scarce to
rare, but not because it was not struck. Quantities were smaller than gold or copper because of the coins' awkward place in the economy, but they were struck throughout
Byzantine history: siliquae and fractions in the early period, "hexagrams" during the Heraclian dynasty,
miliarense and fractions during the middle period, and
stavrata and fractions in
the late empire.
One explanation for the scarcity of coins in the early and middle periods of
Byzantine history is simply that the
Byzantines had a less advantageous exchange rate for silver to gold. That meant that almost as soon as silver coins were struck they were smuggled to surrounding arab/persian neighbors, exchanged for gold, which was then smuggled back and exchanged for silver. The more turnaround, the greater profit. This, plus smaller minting in the first place, makes
Byzantine silver very
rare and desirable today.
BTW, the silver content of most
billon issues is practically non existent. If you were to do a spectral analysis of most "
billon" coins, you would find that they are mostly copper and tin.
--Chris Connell