I would suggest reading the Mining FAQ in the Data Chest sub-forum of this forum.
Ore type DOES NOT come into play for skill gains from the actual MINING of ore. You can get all the way to GM mining only iron.
Ore type only affects Mining skill gains from SMELTING the ore after you mined, and at 95 skill you can get gains from smelting any ore Copper and above (in other words, you have to be able to fail on smelting to get a gain). Smelting the medium to high ores one piece at a time is your best bet on gains from smelting.
By the way, I think you are underestimating how long you've been gone, or at least how long it's been since you mined. Next month is the EIGHTH anniversary of the ore vein randomization (which happened in August 2007). In fact, we've had randomly changing colored ore longer than we've had colored ore, if I remember how long it was after UO launch that colored ore was introduced (well before my time - I started with AoS, myself)