Black Stuff on Rocks

9/27/2014

Someone recently asked me about some black stuff he was seeing on rocks. I noticed this one today and did a bit of research. I thought it worth sharing. The following explanation comes from eHow.com:
"Crustose lichen is the only plant that will grow on a bare rock. This is accomplished by gathering small amounts of water and then in winter when the water freezes, it cracks the rock surface, providing the lichen with minerals and organic materials. Over time this process forms a tiny bit of soil on the rock. These lichen tend to lay flat on their host, looking much like paint splatters, making them hard to remove. They range in color from black, gray, brown, orange, yellow and green. About 75 percent of all lichen in the world are crustose lichen. When dating stone walls and gravestones, scientists measure the radius of this lichen growth since it grows so slowly and lives for centuries."

Read more : http://www.ehow.com/info_8463741_types-lichen-grow-rocks.html

1 Comment

Heather Hodge

2/11/2022 12:12:32 pm

Thanks for this! I've recently become curious about the rocks in my yard and started researching into what they are. What I've found so far is that rock identification is much more complex than I ever imagined! It doesn't help matters that the majority of rocks I'm wanting to identify are highly metamorphosed and vary from one to the next.
I live right beside a creek and my yard is full of rocks of all different types. I can only assume that the creek actually ran through my yard at some point in the distant past..at least the part that is densely populated with rocks. (That also happens to be the part closest to the creek, which is actually across the street..it bends right in front of my house, so it goes straight in front of my house and turns and continues down along the side).
The most intriguing rocks are mainly white in color & most faces reflect light almost like a moonstone...at a certain angle the entire face will practically light up. While some of these white rocks can be mainly solid white to clear, most have fractures with different colored inclusions ranging from grey to yellow, orange, red, purple, pink...and I've noticed that most are weakly magnetic along the fractures.
Anyway, I'm getting off topic here...also there are several of the larger white rocks that have black growths like you spoke of...like paint splotches. It seems like the black growths are on faces that are above ground, at least as far as I've been able to tell. (I've dug some up and don't believe I've found any black on the parts that were buried). I wondered if it was a type of fungi and after seeing this post I feel a little more certain that's what it is.
Idk what state this site is affiliated with, but I live in central NC. I wonder if you're in NC as well since you've got the picture with cardinals..(NC state bird).

Black Stuff on Rocks

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