What is a good home station for mining low temp diamonds?

Setting up a long-term base of operations for mining isn't really that good of an idea. Mining hotspots become depleted the more they get mined out, so your yields will decline over time. Additionally, the selling price of the material you're mining will go down as the station that is buying receives its demand. What I recommend instead is looking for a medium term base of operations, which will shift pretty regularly.

/r/EliteMiners has a good tool to help find good hotspots with good prices here, which I used to get my Elite trade rank.

At the moment, the tool indicates that there is a good spot to mine Low Temperature Diamonds in Borann A2 ring B 123.06 LY from Sol, and a good spot to sell at Noon Orbital in Goibniugo 46.59 LY from Borann, however, this information will shift based on the depletion of the hotspots and the sale price at Noon Orbital.

Be advised though: player pirates will also use this information to plan interdictions. Fly safe.