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MARKETABLE SECURITIES (Tables)

3 Months Ended

Mar. 31, 2023

Cash and Cash Equivalents [Abstract]

The following table summarizes our marketable securities by significant investment categories as of March 31, 2023:


	Cost Basis		Gross Unrealized Losses		Gross Unrealized Gains		Fair Value
Marketable debt securities(1)	$	59,359	$	—	$	72	$	59,431
Convertible note(2)	59,457		(198)		—		59,259
Marketable equity securities	2,876		(1,869)		—		1,007
Total marketable securities	$	121,692	$	(2,067)	$	72	$	119,697

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

(2) The Convertible note was received as 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.