To get this, you need to mine 50 of the same mineral in succession. Below station Gamma, there is a 3-row thick layer of Ironium with plenty of blocks to do this. However, your cargo hold will be too small to hold 50 minerals until you max out the upgrades for it. The final upgrade costs $1 million.
Chains are reset if you mine a different mineral or if you return to the station and empty your cargo.