Toller, soft sand, where the term "Black" is a mystery

Unlike the other reviewers I have to gravel neither washed nor rinsed - any turbidity had disappeared overnight and the shrimp, fish and crabs hats not yet harmed.
The sand is very soft and erstklssig suitable in the water for shrimp that always edit the top layer ground a little.

Why the sand has the name "Black" is not understandable for me. The mixing ratio of black and white grains is felt at 2: 1. If the gravel wet, it gets a little better, but dry it is just gray. Available here about as different batches? A pity ...