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What type of rock is this? It's sold as poultry grit and says granite on the bag, but I want to be sure.

pebbles with scale

pebbles close up

Canadian Quarter (Ø = 23.88 mm) shown for scale.

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Yes, based on the photo it is granite. Granite is a mix of quartz, feldspar, mica, and amphibole minerals.

While I can't see any mica, the grit appears to be coarse grained (crystalline fracture and cleavages), and composed of quartz and feldspar. Acidic granites typically are lighter in color than alkaline granite which is will be composed of alkaline feldspar which are typically darker in color.

I have seen granite in Black Hills of South Dakota or North Carolina that match your photo.

Reference: https://en.wikipedia.org/wiki/Granite; I read through the Wikipedia entry and it is a decent definition.

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