Table 1. Modal Mineralogy of Iceland Samples as Determined by XRD Peak Area Fitting and Rietveld Refinement


Sample	Description (Figure)	Qualitative Spectrally Determined Mineral/Structural Element	XRD-Determined Mineralogy
VNIR	TIR	Pyroxene	Plagioclase	Ilmenite	Hematite	Smectite	Cristobalite, Quartz	Quartz	Celadonite	Zeolite

hvalfj011	gray, fiable rock (1d)	HCP + Fe/Mg smectite + (chlorite?)	H2O-bearing, altered basalt, high silica phase	34	40	5		17				5 (clinoptilolite)

hvalfj017	reddish friable rock (1d)	montmorillonite + hematite	H2O-bearing, dioctahedral ferruginous smectite		10		10	79				2 (epistilbite)

hvalfj023a	blue-green precipitate in vesicle (1f)	celadonite	celadonite		6			20	35		38	1 (mordenite)

hvalfj025	host rock from rock with vesicles with blue-green precipitate (1f)	HCP + hydrated phase (FeOH-bearing?)	H2O-bearing, altered basalt, nontronite	38	49	1	<1	11				

hvalfj054	host rock from rock with vesicles with whitish precipitates (1g)	HCP + Mg smectite	H2O-bearing, altered basalt, high silica phase	63	5		5	17				9 (levyne) 1 (stilbite)

hvalfj055a	opaque white to cream precipitate in vesicle (1g)	thomsonite (+ other zeolite?)	(thomsonite?)					8				36 (scolecite or mesolite) 30 (thomsonite) 26 (stilbite or stellerite)

hvalfj057a	transparent white crystalline precipitate in vesicle (1g)	analcime	analcime					33				55 (analcime) 11 (stilbite or stellerite) 1 mordenite

icel009	massive brown rock with greasy feel (1e)	HCP + Fe/Mg smectite	H2O-bearing, altered basalt, high silica phase	26	49	1	<1	23				

icel010	massive black rock with greasy feel (1e)	HCP + Fe/Mg smectite	altered basalt	28	49	3		20				

wtrfall016a	white precipitate from vein (1g)	hydrated silica	quartz, cristobalite		2				3	91		4 (clinoptilolite)

aFrom vesicle or fracture fill rather than the bulk rock.