Just to sate my curiosity, I made a new game at default settings (500m pop) and calculated the cost of every facility on the planet in minerals. I just did aggregate minerals and didn't compare by type, but the total mineral cost of everything (including the military and commercial shipyards with costs for capacity and slipways) came out to only 231,510. You would have to start with a very very large population to be assigned enough facilities to be worth a few million minerals. The minerals on the world (including the already mined stockpiles) were 644038. You also have fuel, and free points for ships (fast OB creation), and maybe a bit of commercial usage in the years prior to starting, bringing it to about a million minerals used or currently on the earth all total.
That same game has Venus, a slightly smaller planet, with roughly 13 million minerals (which is actually very low for Venus, my other game had 110 million, the one before it had about 80 million IIRC). Mars has 22 mil. Even Luna has about 2.5 million, and it's 1/4 the size. Mercury is barren, but you can't have everything.
That's quite a difference compared to the measly 1 mil I attributed to Earth.
I wouldn't really say it has "far more than random chance says it should have." Sure, it has 11 types, but the low quantities make it fairly short-lived - and just randomly generating gives a good mix of minerals for Earth it seems. Does the mineral generation routine run by tapping the "All Minerals" button (SM mode) generate it just like a normal game? By the description of the button I assume it does. I did a bit of testing just out of curiosity and the first time it generated earth with a whopping 193 million minerals with 10 varieties (missing one). A second push of the button gave me 145 mil with 8 varieties. A third was 113m with 9 varieties. Fourth came out 167m with 10 varieties. Fifth came out 43m with only 6 varieties. Sixth was 123 mil with 7 varieties. I stopped counting after that, but tapping the button another 30 times never once showed the earth as no minerals.
Maybe having 1.0 gravity gives 100% chance of minerals? Venus almost always has a good assortment of minerals too, but not quite as good as Earth - it has 0.91 gravity. I deleted my colony there and reran it with nothing just in case colonies influenced the mineral generation, but it didn't seem to have an effect. Now the availability of these are often low, but in some of the cases it was good. The time with 167 and 10 varieties had 9 of the minerals at 0.5 or above, with the 10th at 0.1.
The low minerals kinda makes sense from a gameplay perspective if you want to get the player in a mineral crunch and make them branch out rather than just holing up for 100 years on Earth.
It just doesn't make much logical sense. Maybe I'm nutty, but I think about things like that when playing games. Even if the Earth in these games was always generated with low minerals at say 10 million, where did the humans put the other 9 million minerals that should have been on the planet? That's a lot of minerals to have been mined out and mysteriously used.
Hmm, maybe I should post in the suggestion forum...