ASTM C217/C217M-15a

1.1 This test method covers two procedures for weather resistance of slate in all outdoor installations by determining the depth of softening by shear/scratch tester or by hand scraping.

Note 1: The test is based on the fact that slates containing pyrite, calcite, and carbon undergo a chemical weathering which results in the conversion of the calcite particles to gypsum. The swelling action that results causes disintegration of the slate. The extent of this action on various slates in the test has been found to correlate with the durability of the materials in actual weathering.