Granted Patent
Utility
US 4,440,569 · App. 06/468,740
Recovery of zinc from zinc-containing sulphidic material
Inventors:
Donald R. Weir, Ian M. Master
Patented Case
View Patent ↗
Granted: Apr 3, 1984
Filed: Feb 22, 1983
Inventors
Donald R. Weir
Ian M. Master
Assignee (at issue)
Sherritt Gordon Mines Limited
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.