I found this rock in a glacial till in north central Washington State, on the east side of the Cascade Range. The dark round crystals are roughly 1 inch (2.54 cm) by 2 inch (5.08 cm) in size. The center of the lowest point of erosion zone is mid slope but not near the other larger heavier boulders that stopped at the toe of slope change. The rock itself is nearly three feet long (91 cm) and fourteen inch diameter (35.56 cm) and only two of these exist on strata surface. This was likely uncovered from recent post wildfire flooding. The rock attracts a magnet from nearly two feet (61 cm) away.



closed as off-topic by user12525, Erik, Jan Doggen, trond hansen, Gimelist Aug 27 at 10:05

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  • $\begingroup$ Did you take only one picture? Nothing else you tried 'with' the rock? $\endgroup$ – Jan Doggen Sep 28 '15 at 6:34
  • $\begingroup$ I took more pictures, but couldn't figure out how to load more than one. If you mean, is the rock itself magnetic, I didn't try anything, with, the rock. $\endgroup$ – Brandon Sep 29 '15 at 4:05
  • $\begingroup$ If you cannot edit more pictures into your question (not enough reputation yet?), put them on an external image hosting site (postimg, imgur) and add the links to your post. Someone else will edit it further and pull them in. $\endgroup$ – Jan Doggen Sep 29 '15 at 7:25
  • $\begingroup$ See this guide for ways to improve this question. $\endgroup$ – naught101 Nov 3 '15 at 2:11
  • $\begingroup$ Could you post a more precise location or link to google map location? Thanks. $\endgroup$ – haresfur Mar 16 '17 at 3:57

It's not possible to tell what it is from this photograph, but from the limited information given, my first guess is a coarse grained gabbro with large phenocrysts of pyroxene.


There are only a few places in the world where one finds "orbicular granites" like in this australian web photo:

enter image description here

What you may have found is it's mafic equivalent: an ophitic basalt (or gabbro) in which large pyroxenes enclose feldspar cores. They're common enough in mafic igneous bodies, but yours are seriously on steroids!

Of course, without seeing any detail, your rock could be sedimentary in origin....in which case it could be just a weird magneto-conglomeratic pile of dinosaur doo-doo :)


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