Belters has never been given much attention in Traveller other than in Beltstrike and maybe in the adventure "Expedition into Zhodane"
The only function I see for a mining laser is to cut asteroids or large rocks into smaller ones that are gobled up by ships/robots of different sized and crushed to smaller pieces before large ovens melts the ore out of the collected rocks.
Lasers simply replaces the need for use of explosives to break chunks of rocks apart. No one in their right mind would blow a rock into pieces. It will send shrapnel all over the place, and it my damage both crew and equipment. On a planetary surface this is of minot concern as gravity and air resistance will make sure that shrapnel from blasts doesn't fly too far.
With this in mind I suspect a mining laser will have way different properties than a weapon grade laser. Much like a over sized surgical laser. Instead of steady pulses it sends a continous beam that burns through the rock. The effect is also relatively low compared to weapon grade lasers. neither gravitic focusing or a-ray technology is required as ranges are usually just a few hundred meters at most.
I expect a focal array for a continious laser beam is will have different properties than a weapon grade laser. Effect may be limited to just a few MJ.
Finding ore would probably be done with a wide variety of sensor scans. Both to find asteroid density and mass. Knowing these things will help determine if there might be anything valuable inside. Deeper scans with earth penetrating radar or just landing and do seismic tests may reveal other properties. And lastly chemical and spectroanalysis. This can be done by using the mining laser.
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Roger Malmstein
www.travellerfreeport.com