drossless

From dross +‎ -less.

drossless (comparative more drossless, superlative most drossless)

1. Free from dross.
   • 1791, William Bagshaw Stevens, "to the author of the poem on the loves of the plants" (prefixed to Erasmus Darwin's The Botanic Garden)

     OFT tho' thy genius, DARWIN! amply fraught
     With native wealth, explore new worlds of mind;
     Whence the bright ores of drossless wisdom brought,
     Stampt by the Muse's hand, enrich mankind;