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MARKETABLE SECURITIES (Tables)

6 Months Ended

Jun. 30, 2023

Cash and Cash Equivalents [Abstract]

The following table summarizes our marketable securities by significant investment categories as of June 30, 2023:


	Cost Basis		Gross Unrealized Losses		Gross Unrealized Gains		Fair Value
Marketable debt securities(1)	$	63,019	$	—	$	212	$	63,231
Convertible note(2)	59,457		(251)		—		59,206
Marketable equity securities	2,876		(1,987)		—		889
Total marketable securities	$	125,352	$	(2,238)	$	212	$	123,326

(1) Marketable debt securities are comprised primarily of U.S. government agency bonds.

(2) The Convertible note was received as partial consideration in the Alta Mesa Transaction (defined in Note 5 – Property, Plant and Equipment and Mineral Properties) and is valued using a binomial lattice model using Level 3 inputs. See Note 5 – Property, Plant and Equipment and Mineral Properties and Note 13 – Fair Value Accounting for more information.

The following table summarizes our marketable securities by significant investment categories as of December 31, 2022:


	Cost Basis		Gross Unrealized Losses		Gross Unrealized Gains		Fair Value
Marketable debt securities(1)	$	11,435	$	(310)	$	—	$	11,125
Marketable equity securities	2,876		(1,809)		—		1,067
Total marketable securities	$	14,311	$	(2,119)	$	—	$	12,192

(1) Marketable debt securities are comprised primarily of U.S. government agency bonds.