What is this??

Asked July 17, 2019, 12:59 PM EDT

Having a hard time identifying this “rock”

Outside United States geology

3 Responses

Pretty rocks! Without knowing where they were collected, it's a bit of a guess. They appear to be glassy in texture, filled with vesicles (air bubbles). At a guess, it looks like a vesicular portion of an obsidian flow. Obsidian flows are a volcanic lava that flows very slowly. A prime example is the Big Obsidian flow in Newberry Crater, central Oregon.https://en.wikipedia.org/wiki/Newberry_National_Volcanic_Monument

Gas is present in the molten lava. The gas bubbles tend to move up through the lava flows, creating "froth" on the top of the flow, or bands of bubbles scattered through the chilled deposit. These rocks suggest that type of environment.
You didn't mention the weight but I suspect these rocks are not heavy, compared to other rocks of a similar size. Obsidian, volcanic glass, is not a dense rock.https://en.wikipedia.org/wiki/Obsidian
Nice collection of rocks!

I’m in Ontario, Canada.
It was just one rock that I decided to break open out of curiosity.
it is super light and there are some black specks in it that are magnetic.
Thanks for your help

<grin> Thank you for the "rest of the story"! Magnetic black specs also fit the scenario. Another odd scenario would be a discard from past industrial activity where rocks have been altered by heat. If you picked it up where historic/past industrial processing occurred, it might also account for the bubbly glassy nature of the rock. But I suspect, it's the first theory. Good question and a fun mystery rock!