IODP SEDIS - Thesaurus -

opal
BT	silicates
	.framework silicates
	..silica minerals
	...opal
NT	opal-A
	opal-CT
UF	opaline
RT	floatstone
	hyalite

opal A
USE	opal-A

opal-A
BT	silicates
	.framework silicates
	..silica minerals
	...opal
	....opal-A
UF	opal A
RT	amorphous materials
	opal-CT
SN	Amorphous, biogenic opal.

opal-CT
BT	silicates
	.framework silicates
	..silica minerals
	...opal
	....opal-CT
RT	opal-A
	cristobalite
	tridymite

opaline
USE	opal