Ore processing in IC² is a multi-stage process, requiring several machines in order to get the maximum possible yield from each individual ore.
The best ore yield comes from a three-stage process. The first stage is a necessity; the second or third may optionally be skipped, but will reduce yield.
A Macerator processes ore - iron, gold, copper, tin, lead, and uranium - into 2x crushed ore of the corresponding type.
It does not process (as of 2.6.130-ex110) ores for coal, lapis, diamond, redstone, emerald, or nether quartz.
Crushed ore can be smelted into ingots (except for uranium).
Purified crushed ore can also be smelted into ingots (again, except for uranium).
A Thermal Centrifuge processes purified crushed ore into dust (except for uranium yet again), with another secondary product.
Dust is the final pre-smelting state and requires no further processing, though it may have other uses (creating alloys like Bronze for example).
Ore washing (stage 2) may be skipped (the red final column below), in which case the centrifuge (stage 3) will also yield Stone Dust in addition to its usual products (which the ore washer would normally have produced). However, the tiny ore dusts from stage 2 will be lost in doing so, and in some cases other yields will be reduced as well.
Full 3-stage processing is therefore highly recommended in order to get the most out of your ore.
Note that silver ore is not generated by IC²; however, any properly defined
oreSilver can probably be macerated into crushed silver ore and processed accordingly. (If it can't, perhaps you should let a dev know. Politely.)