A major impact on mineral generation is System Abundance. This is generated randomly, but is significantly affected by the age of the star. Younger systems will generally have better mineral deposits. The first thing I always check on a new system is the age of the star and I prioritise younger systems for geological survey.
There are six system abundance values from 1.5 to 0.25 in decreasing 0.25 increments. There is a roll of (D10 + D10 + System Age), with the abundance assigned on results equal or less than 12, 14, 18, 21, 24 and 30. The abundance is used as a modifier to the existence of minerals in general and the existence of each mineral type on a body. The amount and accessibility are based on body size.
So, a simple way to change the amount of minerals in real stars games would be a modifier (+1, +2, etc.) to the System Abundance roll.
Thanks for the insight into mechanics. Is abundance values (1.5 to 0.25) here just a straight modifier on quantity of minerals found only? (or does it impact chance of each mineral appearing and acc. level rolls too?). And doesn't younger systems having more abundant minerals imply that a lower roll is better? (why would you then add +1 or +2 to it?)
Is there also a reason for limiting it to real stars? It could be interesting to be able to play a non-real stars game with less minerals also for me (if the modifier works both ways ranging from for example -4 to +4 or which levels seem reasonable). Ideally there should always be a small chance of having the highest system abundance.
Either way adding something for this would help alot! I would greatly appreciate if you can consider adding a dropdown or some way to tweak it next time your fiddling with game creation settings
Min Abundance is used in both real and random stars. Min generation is better in the latter because there are more luminous stars. Stellar Types F, A and B, plus giant stars tend to be younger, so better minerals. Yes, should be -1, etc. for improved minerals.
Abundance Roll is as described above. Abundance is doubled for bodies in the life zone. The life zone in AU is between= 0.75 * Luminosity^0.5 and 1.4 * Luminosity^0.5
Any Radius below 100 km is treated as 100 km.
The percentage chance of a body having minerals is Abundance * ((Body Density * 10) + (Radius / 100.0)).
An Earth-sized planet in the life zone would be: Abundance * (10 + 60) * 2. A Mars-sized planet outside the life zone with 0.7 density would be: Abundance * (7 + 34).
If a body has minerals, each individual mineral is checked, based on: Density * Abundance * 30 (constant). So Earth would be 30 * Abundance for each mineral. Mars would be 21 * Abundance. Duranium has a x2 modifier for this check.
For each mineral that exists, the amount and accessibility is randomly generated with greater radius improving the former and decreasing the latter.
The only downside to having an Abundance Modifier in game settings is explaining its effect. I guess it could be done in description terms instead of -1, -2, etc. Improved Minerals, Abundant, Scarce, etc.
Another option would be having a 'younger stars' modifier, instead of an abundance modifier. Same effect, but easier to understand.