Table 2.

Summary of soil properties for both calibration and independent validation set for hit quality index spectral subspaces.

Subspace	Variable	Units	n	Min	Max	Mean	s.d	%CV	n	Min	Max	Mean	s.d	%CV
Halloysite
	Clay	%	13	35.26	92.72	78.3	16.6	21.2
	m3.Al	ppm	13	345.8	2242	1309	520.4	39.8
	m3.Ca	ppm	13	133.3	1011	469.7	249.2	53.1
	pH	–	13	5.21	6.38	5.8	0.3	5.2
	Sand	%	13	2.71	21.9	10.1	6	59.4
	Totalcarbon	%	13	0.11	1.69	0.6	0.4	66.7
Illite
	Clay	%	1098	1.1	99.27	45	22.5	50.0	418	8.53	100	46.4	22.7	48.9
	m3.Al	ppm	1098	1.67	2722	898.1	474.5	52.8	418	14.3	2240	867.5	428.9	49.4
	m3.Ca	ppm	1098	29.26	35,200	2170.8	3995.8	184.1	418	0	11,000	943.4	1420.1	150.5
	pH	–	1098	3.61	9.27	6.3	1.1	17.5	418	4.01	9.43	5.9	1	16.9
	Sand	%	1098	0.12	98.9	36.7	24.5	66.8	418	0.12	100	35.2	22.9	65.1
	Totalcarbon	%	1098	0.13	11.29	1.5	1.5	100.0	418	0.08	9.4	1.2	1.2	100.0
Montmorillonite
	Clay	%	90	10.96	97.3	65.3	18.9	28.9	24	25.71	100	72.8	15.9	21.8
	m3.Al	ppm	90	424	3041	925.9	388.2	41.9	24	430	1530	760.8	281.2	37.0
	m3.Ca	ppm	90	104	14,858.3	5961.7	4005.6	67.2	24	1130	7570	3704.6	1634.5	44.1
	pH	–	90	4.39	8.98	7.3	1.1	15.1	24	4.98	9.72	7.1	1.1	15.5
	Sand	%	90	1.65	85.26	18.1	16.6	91.7	24	1.38	67.55	14.5	14.2	97.9
	Totalcarbon	%	90	0.25	2.68	1.1	0.5	45.5	24	0.24	3.22	1	0.6	60.0
Quartz
	Clay	%	128	0.32	55.71	20.9	11.6	55.5	133	3.3	25.5	12.8	5.3	41.4
	m3.Al	ppm	128	106	1360	445.7	196	44.0	133	60.9	593	300.4	99.7	33.2
	m3.Ca	ppm	128	58.2	1725	364	287.8	79.1	133	31.8	1700	364.6	256.8	70.4
	pH	–	128	4.32	8.05	5.9	0.7	11.9	133	4.72	9.86	6	0.7	11.7
	Sand	%	128	21.27	99.68	59.9	19.5	32.6	133	42.54	93.89	78.3	9.6	12.3
	Totalcarbon	%	128	0.11	1.02	0.4	0.2	50.0	133	0.09	0.95	0.3	0.1	33.3