Oh man, corundium is used to make beam weapons too!
Used for both lasers and mining lasers!
At least that's my headcanon.
That makes so much sense!
But not to worry, in just under a year, our troubles will be over. Two mines and a mass driver will be unloaded onto Minerva's sixth moon, which has 7.8Mt of corundium (at accessibility 0.1):
In other news, the geosurvey probe we left at Luyten 726-8 A II a few decades ago finally broadcast its results. There are good quantities of three minerals (but no duranium or corundium) to be had there, and there is a ruined outpost and a dormant construct. And you'll recall that last year the probe at Luyten 726-8 A I found good quantities of four minerals (no duranium, but there is 200kt of corundium) and a dormant construct. That's two in one system, and only one jump from Earth! As soon as my flagship is built, I'm going to personally lead the fleet over there to brush aside the alien ship that shot down our diplomatic mission 5 years ago and claim the world for Humanity.