Another possible strategy (I play conventional starts), which must be played from the beginning, is to combine civilian mining and regular colonies.
Initially, I only survey bodies that are good for colonization: Luna, Mars, Mercury, and possibly some of the larger gas giant moons.
At game start, I immediately start enlarging my naval shipyard and when it's big enough (roughly 3000 tons), I build a survey vessel with conventional rockets, conventional geosurvey equipment and a tiny cargo space. Slow and primitive but adequate for this task.
I then survey those few bodies, and if any has the potential to spawn a civilian mining operation, I leave it untouched and dump 2 infrastructure on an empty body. This unlocks the creation of civilian mining. Then I push my wealth income as high as feasible with financial centers and accompanying research, to increase the chance of triggering a civilian mining center. Once it is in place, which is why I initially restrict my initial surveys to places I want the mining colonies to spawn, I add a regular colony to it.
If you build a regular colony, no new Civilian mining centers can spawn. But once the first civilian mining center is in place, it will expand over time, adding up to the equivalent of hundreds of automines. Plus you get a free military unit to keep order.
Civilian mining centers spawn if the body contains Duranium or Gallicite, minimum 10,000 units with concentration 0.7 or more. Higher wealth income increases the spawn chance.

Here's an old detailed thread with worker count mechanics: https://aurora2.pentarch.org/index.php?topic=12258.0

Since Io's colony cost is 6.2, you will need to either use terraforming to get your CC below 5 or deploy orbital habitats. This is because the proportion of your population working in the manufacturing/mining sector will over time drift towards (25-5*colonyCost)%. This means that it is possible to have your worker pool shrink over time even as your population increases.

• A 0 CC home world will eventually settle into 25% of its population as TN workers
• A 2 CC plant will have 15% as TN workers
• A 5 CC plant will have 0% as TN workers

A couple of implications which may be relevant for OP and others:

• With a small amount of calculus, you can find that the peak manufacturing population occurs for a (total) population in billions of P = (0.76 - 0.04*C)^4, where C is the colony cost. For an Io colony cost of 6.2, this means the maximum manufacturing population will occur for a total population of about 69 million (nice!).
• For a colony cost less than 5.0, once you reach a population of about 240 million the services sector hits a maximum of 70% and manufacturing population increases linearly with total population. This means that, in theory, growing a colony with C < 5.0 will eventually allow you to exceed the maximum manufacturing population from the previous point, although for higher colony costs this may not be economical and the "lower maximum" may be a more realistic target. I would say colony cost of 3.0 or 3.5 roughly marks this boundary, but it depends on how willing you are to invest in growing a population beyond 240 million.
• A colony with C > 5.0 has a hard maximum manufacturing population, and you should not grow it beyond this point. In practice, you probably want to be within a couple million population in either direction and draw off pops/infrastructure from normal growth every so often to maintain the level. This rule applies for Io!
• For a colony cost less than 1.5, manufacturing population will always increase with total population.

Since ark modules do not have any agricultural population, the rules work a little bit differently, but suffice to say since the colony cost factor disappears you will always gain manufacturing population when expanding an orbital (total) population. Since Ark Modules cost a bit more than 500 infrastructure per million population, this means that Ark Modules are probably the most cost-efficient way to support a population for a colony cost greater than 5.0; for lower colony costs it depends on the relative importance of the infrastructure costs vs improved population efficiency, but probably a colony cost of 4.0 is a good approximate break point as a rule of thumb. I would therefore recommend using orbital populations to colonize Io if you have researched and built Ark Modules.

I'm in a similar situation, with Io having many interesting minerals. I settled it and let it develop around 2 M, and then it kicked automatically, with civilian freighters transporting extra infrastructures and then pop.
I'm basically doing nothing and it is already at 11 M.

Hi all, just thought I'd ask the collective wisdom about some potential decisions

I've been fortunate enough to get a lot of minerals on Io - enough with other in system resources to help sort out the potential minerals crunch - in particular 3m (1) Duranium, 1m(0.9) Vendarite, 2m(0.4) Corundium and 3m(0.4) Gallicite.

Now how best to extract? I'm currently establishing a ground colony (6.2 CC) and relying on injecting greenhouse gas to get the temp up and the CC down, but I could automine or use an orbital habital I suppose. Bear in mind I want a really substantial mining operation here, to get all those lovely minerals out of the ground.

How would others suggest?

Legemaine

Hi JacenHan, thanks for this. You were right - that's what I had forgotten.

Playing Aurora is NOT like riding a bicycle - you certainly can't just pick up where you left off. But it probably wouldn't be as engrossing if you could

Regards