What do you mean 3rd? STEEM has been on OpenLedger practically from the start. CMC currently lists 4 exchanges with multiple STEEM markets: https://coinmarketcap.com/currencies/steem/#markets
That said, more exchanges won't hurt. Although I question if Vircurex is a wise choice. They've been hacked ~2 years ago and are still pretending to pay back the stolen funds...