10. Property, Plant and Equipment, Net

The components of property, plant and equipment are as follows:


	September 30,		December 31,
	2019		2018
	(in thousands)
Mineral properties	$	9,353	$	9,353
Exploration properties		2,518		2,518
Royalty properties		200		200
Buildings		3,755		4,278
Mining equipment and machinery		16,038		16,024
Other furniture and equipment		884		888
Asset retirement cost		866		866
		33,614		34,127
Less: Accumulated depreciation and amortization		(27,310)		(27,018)
	$	6,304	$	7,109

Celaya Farm-out

In August 2016, the Company, through its wholly owned Mexican subsidiary, entered into an earn-in agreement with a 100% owned Mexican subsidiary of Electrum Group, LLC, a privately-owned company (together “Electrum”), related to the Company’s Celaya exploration property in Mexico. The Company received an upfront payment of $0.2 million and Electrum agreed to incur exploration expenditures totaling at least $0.5 million in the first year of the agreement, reduced by certain costs Electrum previously incurred on the property since December 2015 in its ongoing surface exploration program. Electrum initially earned the right to acquire an undivided 60% interest in a joint venture company to be formed to hold the Celaya project by incurring exploration expenditures totaling at least $2.5 million during the initial first three years of the agreement. Electrum would serve as manager of the joint venture. Prior to subsequent amendments to the agreement, the Company would have been allowed to maintain a 40% interest in the Celaya project, following the initial earn-in period, by contributing its pro-rata share of an additional $2.5 million in exploration or development expenditures incurred over a second three-year period.

In February 2018, the Company and Electrum amended the Celaya earn-in agreement to permit Electrum to earn, at its option, an incremental 20% interest in the Celaya project in exchange for a payment of $1.0 million. Following the amendment, Electrum could have increased its total interest in the project to 80% by contributing 100% of the $2.5 million of additional expenditures required in the second three-year earn-in period. Following the second earn-in period, and prior to the Company entering into a second and final amendment of the agreement, the Company could have maintained its 20% participating interest or its interest could ultimately have been converted into a carried 10% net profits interest if the Company elected not to participate as a joint venture owner.

In September 2018, the Company and Electrum entered into a second and final amendment of the Celaya earn-in agreement pursuant to which Electrum acquired 100% of the Company’s remaining interest in the Celaya project in exchange for a payment of $3.0 million. The transaction was set out in a definitive Assignment of Rights Agreement (the “Assignment Agreement”) containing customary terms and conditions. The earn-in agreement was terminated upon entry into the Assignment Agreement.

The Company had previously expensed all of its costs associated with the Celaya property and accordingly recognized a gain of $1.0 million from the execution of the first amendment to the agreement in the period ended September 30, 2018, included in “Other operating income, net” in the accompanying Condensed Consolidated Statements of Operations. The Company recognized a gain of $3.0 million from the execution of the second amendment to the agreement in the nine-month period ended September 30, 2018.

Zacatecas Farm-out

In April 2016, the Company entered into an option agreement, which was later amended in February 2018, under which Santacruz acquired the Company’s interest in the Zacatecas Properties for a series of payments totaling approximately $1.5 million through October 2018, including $249,000, $225,000 and $212,000 paid to the Company during the first, second and third quarters of 2018, respectively. The final payment due the Company of $13,000 was received in October 2018. Upon receipt of each cash payment, the agreement imposed a performance obligation on the Company to provide Santacruz an exclusive right to the Zacatecas Properties to conduct exploration activities during the period from receipt of the payment until the next payment due date, with a final obligation, following receipt of the final payment, to formally acknowledge completion of the sale enabling Santacruz to register title to the properties in its name. At December 31, 2018 there were no further performance obligations and the Company had taken all steps necessary for Santacruz to take title to the properties.

The Company previously expensed all of its costs associated with the Zacatecas Properties. Because Santacruz was able to terminate the option agreement at any time, and the associated uncertainty relating to timely payments, the Company only recognized income, equal to the cash payments made, evenly over the period covered by each payment. The Company recognized approximately $336,000 of income under the agreement for the nine months ended September 30, 2018, included in “Other operating income, net” in the accompanying Condensed Consolidated Statements of Operations. The Company also recorded a liability of approximately $225,000 at September 30, 2018 representing its unearned performance obligation related to the agreement, included in “Other current liabilities” as reported in its Condensed Consolidated Balance Sheets.