I saw a patch of black grass near some regular tan-coloured sand, amidst regular green grass. It was weird, and it smudged my fingers black when I picked a blade.
Well I'm not sure, the fact that it left residue really makes me thing it was a large patch of fungus or rot, but it's hard to judge without seeing it haha
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http://bauble.botanicalgarden.ubc.ca/images/2013/fittonia-albivenis-argyroneura.jpg
There's a lot of color variations of this plant. I had one with pink and it was almost the same, except the color.
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https://liquidlawn.com/wp-content/uploads/2017/01/slime-mold-grass.jpg
More like this?
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http://www.kazimingi.co.za/wp-content/uploads/2014/08/Ophiopogon-black-dragon.jpg