SPI Minerals Group

	Element	%		Oxide	%		anhydrite
	O	46.85							This is a reflected light micrograph of polished, carbon coated anhydrite crystals. The identifying etched label, which is a feature of our standards, is invaluable for navigating in an electron beam instrument. Anhydrite has 3 perpendicular cleavages, which explains the rectangular crystals and the triangular cavities in the polished surface. The other common form of Ca sulfate, gypsum, contains water and is unstable in vacuo. Anhydrite, as its name implies, has no water and is therefore more stable, thus making it a good standard for sulfate sulfur. Locality unknown
	S	23.46		SO3	58.58
	Ca	29.06		CaO	40.66
	Sr	0.71		SrO	0.84
	Sum	100.1		Sum	100.1

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Name	Description	SPI #	Each
Anhydrite	SPI SuppliesŪ Individual Mounted Microanalysis Standard Item	AS1030-AB	$199.56