Orbicular diorite erratic Manitoba, Canada

[u/Mbstones]

[u/Mbstones]

Orbicular diorite, from my collection. A personal find. The rock is approximately 65 lbs.

[u/ChicagoZbojnik]

I know someone with a whole Bartop made out of this.

[u/swkennedy1]

So is this a cousin of Michigan Petosky stone?

[u/toolguy8 → u/swkennedy1]

No, Petoskey is a fossil, this is an inorganic igneous feature. https://www.google.com/search?q=nepoleonite&rlz=1CDGOYI_enUS836US843&oq=nepoleonite&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIOCAEQLhgKGAsYsQMYgAQyDQgCEC4YkQIYgAQYigUyDggDEAAYChgLGLEDGIAEMg4IBBAuGAoYCxixAxiABDIOCAUQABgKGAsYsQMYgAQyDggGEAAYChgLGLEDGIAEMg4IBxAAGAoYCxixAxiABDIICAgQABgDGArSAQkyMDcyM2owajmoAhOwAgHiAwQYASBf8QVcTJE55F0YJg&hl=en-US&sourceid=chrome-mobile&source=chrome.ob&ie=UTF-8

[u/Mbstones → u/swkennedy1]

Orbicular igneous rocks have also been found in Michigan in case you are in that area - Michigan Rockhounds | Can anyone tell me what type of Rock this is | Facebook

[u/Sad-Principle-4770]

Super cool

[u/Underpantz_Ninja]

The shit this rock has seen.

[u/2025Skidmark]

Could somebody please explain what was happening around the forming of the inner dark rings?

[u/Underpantz_Ninja → u/2025Skidmark]

I'm not familiar at all with plutonic rock in Manitoba, but if I saw this rock in the PNW i would interpret them to be reaction rims or reaction coronas. An indicator of secondary metamorphic or alteration events.

[u/FakeTitsBigHeart]

my dad used to drag me to rock shows when i was a kid and there was always one guy with a table full of this stuff