Inventories

12 Months Ended

Dec. 31, 2021

Inventories, net

Inventories in the Consolidated Balance Sheets are summarized as follows:


	December 31,
(Thousands)	2021		2020
Raw materials and supplies	$	93,518	$	42,905
Work in process	221,638		156,093
Finished goods	45,959		51,780
Inventories, net	361,115		250,778

The Company takes and records the results of a physical inventory count of its precious metals on a quarterly basis. The Company's precious metal operations include a refinery that processes precious metal-containing scrap and other materials from its customers, as well as its own internally generated scrap. The Company also outsources portions of its refining requirements to other vendors, particularly those materials with longer processing times. The precious metal content within these various refine streams may be in solutions, sludges, and other non-homogeneous forms and can vary over time based upon the input materials, yield rates, and other process parameters. The determination of the weight of the precious metal content within the refine streams as part of a physical inventory count requires the use of estimates and calculations based upon assays, assumed recovery percentages developed from actual historical data and other analyses, the total estimated volumes of solutions and other materials within the refinery, data from the Company's refine vendors, and other factors. The resulting calculated weight of the precious metals in the Company's refine operations may differ, in either direction, from what its records indicate that the Company should have on hand, which would then result in an adjustment to its pre-tax income in the period when the physical inventory was taken, and the related estimates were made.

The Company maintains the majority of the precious metals and copper used in production on a consignment basis in order to reduce our exposure to metal price movements and to reduce our working capital investment. The notional value of off-balance sheet precious metals and copper was $480.2 million as of December 31, 2021 versus $400.0 million as of December 31, 2020.

Amounts for the year ended December 31, 2020 have been revised to reflect a $44.6 million reclassification out of work in process and into finished goods inventory.