If you play smaller maps with many civs placed on it you often are lacking in horses, stone, and copper. The game finds it more important to place oil and iron resources. so it neglects these other strategic resources. the only reason I can find for plenty of marble but little stone is that marble comes first in the xml file. Also sugar and wine are often missing as far a luxury type resources. This is almost certainly because they come last in the xml file.
I wish I know how to adjust the values better to get better maps but I haven't found the right mix yet...
I wish I know how to adjust the values better to get better maps but I haven't found the right mix yet...