3. Revenue

The Company derives its revenue from the sale of doré and concentrates. The following table presents the Company’s net sales for each period presented, disaggregated by source:


	Three months ended March 31,
	2020		2019
	(in thousands)
Doré sales, net
Gold	$	7,683	$	1,683
Silver		676		400
Less: Refining charges		(92)		(38)
Total doré sales, net		8,267		2,045
Concentrate sales
Gold		6,216		4,565
Silver		5,215		3,761
Copper		2,361		2,114
Lead		3,479		3,395
Zinc		9,040		12,271
Less: Treatment and refining charges		(5,835)		(3,410)
Total concentrate sales, net		20,476		22,696
Realized/unrealized embedded derivative, net		(738)		1,837
Total sales, net	$	28,005	$	26,578