Strange rock cracked open

[egarceau]

Hello! I collect rocks as a hobby, nothing serious, and have come across some rocks I just camet figure out. This first one is seemingly uninteresting from the outside, but when I cracked it open was surprised by the black powder and crystals in the center only. Thank you for trying to help me figure this out!

 

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[Geochem]

Hello! I collect rocks as a hobby, nothing serious, and have come across some rocks I just camet figure out. This first one is seemingly uninteresting from the outside, but when I cracked it open was surprised by the black powder and crystals in the center only. Thank you for trying to help me figure this out! View attachment 1400941View attachment 1400942View attachment 1400943View attachment 1400944View attachment 1400945

Hello egarceu, It appears the rock is a courser grain-size granodiorite. The more fresh looking crystals are the basic look of the original rock. The rock outside has went through various weathering processes, and has iron leeched out and oxidized on the out side, the more yellowish outside appearance.

Mother Nature does not make many carbon copies of intrusive rocks, with most having their uniqueness in amount, type, color (impurities in minerals), grain size of each mineral present. What you have appears to be a plagioclase rich granodiorite moderate size quartz and lower concentration of small size amphiboles.



Best to take pictures with real good lighting, like outside or under a white light type lamp.

Keep looking around as you hike. There sould be "contact minerals zones" where the intrusion meets the host country rock. More exotic metamorphic minerals of gem quality can be found at the host rock contacts and along instrusive veins in the host rock.

 

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[egarceau]

Awesome! Thank you for your expertise and helpful advice! I certainly will keep an eye out once the weather gets warmer and I can procrastinate with my rock hunting yet again! (But at least I feel like I'm learning so many new things!)

 

[MrLee]

"Hello! I collect rocks as a hobby, nothing serious,"

Famous words before your house, garage, yard, cars become display areas for your "rock collection".

 

[egarceau]

MrLee you could not have spoken any truer words! Good thing for winter months and snow or our entire basement would be filled! haha!