... do you know for a fact that ivory was not used in Deadwood?

Wasn't Deadwood a prosperous place with the gold and silver mines? If ivory was used it would been brought from the east coast. Now, the question is were the saloon owners transplanted east coast saloon owners?

The only thing I know about Deadwood is what I saw on the HBO series. In the series Wild Bill played with ivory chips. I remember seeing a flowered $1 and $5 chips on the table. HBO usually does extensive research on its period pieces (example: ROME). If they used ivory in the series I would believe that ivory was used in Wild Bill's games.

I even emailed HBO and asked them if they used real ivory in the series. They were fake props.