Reprocessing - EVE University Wiki
Compressed ores require 1 unit to process, while uncompressed ores require 100 units. You cannot process uncompressed ores with less than 100 units of a single type, e.g. 75 units of Veldspar cannot be combined with 25 units of Dense Veldspar for processing. Both compressed and uncompressed ores yield the same amount of minerals per batch.