Assertion: black slate | /r/HasProperty | softer slate roof material
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text: Still, homeowners can choose between the available slate roof kinds sea green slate (a long lasting roof slate that is also known as fading gray-green slate, for its fading color quality due to weathering), purple slate (which keeps to a dark purple color throughout its life), unfading green slate (can last up to 200 years) and Pennsylvania black slate (a softer slate roof material) and others.