4. PROPERTY, PLANT AND EQUIPMENT, NET (Tables)

3 Months Ended

Mar. 31, 2021

Property, Plant and Equipment [Abstract]

Property, plant and equipment

	March 31, 2021			December 31, 2020
At cost:
Mineral rights	$	2,934,951		$	2,955,780
Buildings		63,573,495			64,024,667
Plant and machinery		256,579,799			258,400,710
Motor vehicles		6,507			6,553
Furniture, fixtures and office equipment		3,295,179			3,318,564
Construction in process		18,127,541			12,095,565
Total		344,517,472			340,801,839
Less: Accumulated depreciation and amortization		(176,040,608	)		(173,212,554	)
Impairment		(18,510,233	)		(18,641,596	)
Net book value	$	149,966,631		$	148,947,689