I needed Selenium to get my power plant to grade 4 and stumbled upon HIP 5623 1 on my travels. It's the first planet in HIP 5623, right next to Cubeo. It's not even remotely volcanic but I didn't even know to check for that until recently. I haven't done a lot of surface mining in my time but I can't say I've noticed any difference in terms of MAT scarcity. Maybe I've mostly been on non-volcanic planets.
What I did notice is that planets with nice flat surfaces make me dislike the SRV way less. I was all like 'weeeeeeeeeeeeeeeeeeeee!' as I raced around looking for Selenium. There was also the added bonus that HIP 5623 is closer to Earth's gravity so neither the vehicle or the MATs floated around too much. Though, ironically, I smashed the hull down to a record 20% by the time I had a drip of fuel left because every impact involved a 230mph crash.
I thought I heard a sound coming from behind a rock so I whipped out the Intimidator. It was probably nothing.
It's just a shame I found myself on a completely horrible planet after this while looking for Tellurium so I could finish to grade five. The power plant's finally done though.
I also remembered someone recently mention vertical thrust on the SRV and it took my a while to realise you could actually use the boost button to basically fly above all the crappy terrain. At least on this low G planet. It only took me nearly four years to realise that. 8-o