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Stockholders' Equity (Deficit) - Additional Information (Detail)						3 Months Ended		9 Months Ended
	Aug. 21, 2020 USD ($) $ / shares shares	Aug. 14, 2020 $ / shares shares	Jul. 09, 2019	Jul. 08, 2019 $ / shares shares	Jun. 09, 2015 USD ($) shares	Sep. 30, 2021 USD ($) $ / shares shares	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) d $ / shares shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 $ / shares shares	Mar. 26, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants, exercise price \| $ / shares	$ 4.75
Number of trading days \| d								20
Preferred stock, par value \| $ / shares						$ 0.0001		$ 0.0001		$ 0.0001
Preferred stock, shares authorized						24,984,166		24,984,166		24,984,166
Share-based compensation expense \| $						$ 312,646	$ 105,162	$ 937,939	$ 315,486
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	1,901,985
Sale of Stock, Number of Shares Issued in Transaction	2,553,314
Offering costs paid on sale of common stock \| $	$ 300,000
Net proceeds received from sale of stock \| $	$ 11,300,000							$ 0	$ 11,315,000
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right	0.6
Purchase price of warrant \| $ / shares	$ 4.543
Cover fees \| $	$ 200,000
Poplar Falls LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants, exercise price \| $ / shares						$ 3.99		$ 3.99
Note And Warrant Purchase Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants, exercise price \| $ / shares		$ 4.67				$ 12.00		$ 12.00
Number of warrants						65,625		65,625
Warrants, expiration date		Aug. 14, 2023	Jul. 21, 2021	Jul. 12, 2024
Class of Warrant or Right, Number of Securities Called by Warrants or Rights		131,996
Note And Warrant Purchase Agreement [Member] \| Second Amendment Agreement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants, exercise price \| $ / shares				$ 5.756
Class of Warrant or Right, Number of Securities Called by Warrants or Rights				196,135
2015 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award authorized by board					450,000
Series AA-2 Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, par value \| $ / shares						$ 0.0001		$ 0.0001
Preferred stock, shares authorized						7,223,145		7,223,145
Series AA-1 Convertible Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, par value \| $ / shares						$ 0.0001		$ 0.0001
Preferred stock, shares authorized						8,427,004		8,427,004
Preferred stock Liquidation preference accretion rate								8.00%
Minimum [Member] \| Series AA-2 Convertible Preferred Stock [Member] \| Penelope Mining LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Closing price of common stock \| $ / shares								$ 15.12
Maximum [Member] \| Poplar Falls LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock and warrants sold								551,378
Incentive Stock Options [Member] \| 2015 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award authorized by board					450,000
Additional shares authorized for stock-based compensation								200,000
Incentive Stock Options [Member] \| 2019 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award authorized by board											800,000
Common Stock [Member] \| Incentive Stock Options [Member] \| 2015 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of incentive option granted								With respect to each grant of an ISO to a participant who is not a ten percent stockholder, the exercise price shall not be less than the fair market value of a share on the date the ISO is granted. With respect to each grant of an ISO to a participant who is a ten percent stockholder, the exercise price shall not be less than one hundred ten percent (110%) of the fair market value of a share on the date the ISO is granted.
Maximum aggregate number of Shares with respect to one or more Awards that may be granted to any one person during any calendar year					83,333
Maximum aggregate amount of cash that may be paid in cash to any person during any calendar year \| $					$ 2,000,000
Common Stock [Member] \| Incentive Stock Options [Member] \| Minimum [Member] \| 2015 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Eligible employee threshold percentage								0.00%
Purchase price of common stock percentage								(110.00%)