Riley Freemon

Alumni from the Republic University's Institute of Exploration are known for their daring forays into the most inhospitable biomes in New Eden.

Simple (Veldspar, Scordite, Pyroxeres, Plagioclase)
Coherent (Omber, Kernite, Jaspet, Hemorphite, Hedbergite)
Variegated (Gneiss, Dark Ochre, Crokite)
Complex (Bistot, Arkanor, Spodumain)

Type A
Type A crystals II on a T2 miner has about 44% more yield than a T1 strip miner, which is really nice.
Downside is that you get some residue, which means you cannot get all ore out of an asteroid.

For Type A II your residue chance is 37.6%, which means about 27% of any rock is wasted and you can gain 73% of the ore in it if you mine it all.

Type B
Type B crystals cycle quicker than Type A, which results in 25% more yield.

Residue chance is higher at 64%, which means you can potentially mine 61% of a rock and 39% of the rock is lost.

This means type A crystals can get 20% more ore from a rock (but take longer to do so) and T1 miners can get 64% more ore from a rock (and take even longer).

Type C
Type C crystals are useful when you want to quickly destroy rocks. For example when you want to get rid of less valuable rocks to make Mercoxit respawn in an anomaly, or want to annoy your neighbours.

You destroy rocks 50% quicker than when using type B crystals, which is pretty insignificant, considering you have only 11% of the yield of type A crystals, or 8.8% of the yield of type B crystals, so if you even care about getting some ore at all, type C crystals are useless.

Only if you don’t want to get the ore you’re mining you should consider using type C.