This server-side mod can generate larger deposits, with counterbalance of more rarity.

It doesn't influence probability of ore generation in whole world (I believe globalDepositSpawnRate variable should be used here), rather, if ores are generated in given area, less number of larger deposits will be generated, instead of clutter of many small nodes. Attached pictures shows difference between original and altered ore generation (note than some orange iron ore discs are thicker).

Copper and cassiterite generation is not affected, both deep and surface ones - these small deposits are crucial for initial progress. Also bismuthine, ilmenite, chromite and rhodochrosite generation is untouched.

There are larger but rare deposits or limonite, hematite (magnetite remain original), sphalerite, galena and pentlandite (radius and thicknes may vary randomly, average value mentioned):

• limonite (iron): 4x less, 2x larger surface, 2x thicker, spawn level slightly closer to the sea level, surface nuggets
• hematite (iron): 5x less, 4x larger surface, 2x thicker, surface nuggets
• sphalerite (zinc): 6x less, 16x larger surface, surface nuggets
• galena (lead): 20x less, 16x larger surface
• pentlandite (nickel): 5x less, 4x larger surface
• graphite: 3x less, 4x larger surface, 2x thicker
• sulfur: 5x less, 4x larger surface, 2x thicker, spawn level slightly closer to the sea level, surface nuggets

Additionally, all iron ores (limonite, hematite and magnetite) as well as sphalerite and sulfur, have chance to generate nuggets as indicators. Those usually are unlikely to be spotted on the surface due to limited sensitivity range of such prospecting, but there is chance to find them in caves or sinkholes.

Purpose of this mod is to make slightly harder searching of these order, but with reward as chance of much more rich deposit, once found - instead of "hit and run" (or rather, "dig and run"), player may consider to establish some shelters and other long lasting mining infrastructure.

Acknowledgements: many thanks to Xel for creating block overlay mod, useful for debugging ore generation, and to Th3dilli, creator of FairPlayguardian, which allow to whitelist mods on server ;-)