REVENUES - Additional Information (Details)	12 Months Ended
	Apr. 30, 2021 USD ($) a ft² customer	Apr. 30, 2020 USD ($) ft² customer
Property, Plant and Equipment [Line Items]
Revenues	$ 40,069,000	$ 18,783,000
Percentage of royalty on proceeds	1.42%
Percentage of Royalty, Post Production Costs	1.42%
Public reimbursement	$ 390,000	113,000
Royalties	135,000	608,000
Public improvement district	390,000	113,000
Private infrastructure reimbursement covenants	549,000	324,000
Customer One
Property, Plant and Equipment [Line Items]
Revenues	10,582,000	8,364,000
Customer Two
Property, Plant and Equipment [Line Items]
Revenues	6,606,000	3,105,000
Customer Three
Property, Plant and Equipment [Line Items]
Revenues	$ 4,858,000	$ 2,703,000
Minerals and mineral rights
Property, Plant and Equipment [Line Items]
Surface areas of land held | a	147
New Mexico
Property, Plant and Equipment [Line Items]
Number of customers | customer	4	4
New Mexico | Minerals and mineral rights
Property, Plant and Equipment [Line Items]
Surface areas of land held | a	55,000
Retail Building
Property, Plant and Equipment [Line Items]
Area of land sold | ft²	14,000
Retail Building | New Mexico
Property, Plant and Equipment [Line Items]
Surface areas of land held | ft²	14,000
Amount of sale of buildings and other land	$ 5,493,000
Area of land sold | ft²	14,000
Warehouse and Office Buildings
Property, Plant and Equipment [Line Items]
Surface areas of land held | ft²	61,000	143,000
Amount of sale of buildings and other land	$ 4,000,000
Area of land sold | ft²	61,000