pnw.jack
off to a rocking start
Member since June 2020
Posts: 4
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Post by pnw.jack on Jul 4, 2020 19:36:25 GMT -5
Hey all! First post since my intro, hope all is well! Here's an unassuming rock I found just walking around. I'd like to figure out what it is, mainly due to it's interesting nature when looked at up close. I doubt it's anything fancy or rare, but after some initial studying, here are my guesses: A "Phaneritic" rock. My first guess is Diorite, but could it be Anorthosite Granodiorite Gabbro White bits may be: Feldspar (maybe Potassium Feldspar (Microcline)?) Calcite Anorthite Brown, reflective bits may be: Epidote Dravite Titanite Enstatite Biotite Dark bits may be: Mica Hornblende Thank you very much for your input!! I'll have more later.         |
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Post by rockhoundingwithkids on Jul 4, 2020 19:47:31 GMT -5
I always pick up this stuff and my hubs just rolls his eyes and says it's just granite...my response is always "BUT IT'S SHINY!" LOL
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pnw.jack
off to a rocking start
Member since June 2020
Posts: 4
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Post by pnw.jack on Jul 4, 2020 19:59:17 GMT -5
Ha, maybe's he's right! Hunker.com says
"The most obvious difference between granite and diorite is that diorite usually does not contain quartz, while granite is composed mostly of quartz. ... Granite forms when continental rocks melt together, while diorite is created when various crystals converge with lava below the Earth's surface."
So I guess the question is, is the white stuff mostly quartz or mostly feldspar?
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EricD
Cave Dweller 
High in the Mountains
Member since November 2019
Posts: 1,142
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Post by EricD on Jul 4, 2020 20:48:51 GMT -5
Ha, maybe's he's right! Hunker.com says "The most obvious difference between granite and diorite is that diorite usually does not contain quartz, while granite is composed mostly of quartz. ... Granite forms when continental rocks melt together, while diorite is created when various crystals converge with lava below the Earth's surface." So I guess the question is, is the white stuff mostly quartz or mostly feldspar? In the closer-in photos the white looks very much like quartz to me |
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pnw.jack
off to a rocking start
Member since June 2020
Posts: 4
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Post by pnw.jack on Jul 5, 2020 2:19:13 GMT -5
Thanks so far! I've got a collection of various other fancier things but I'm trying to pin point the more mundane, and really understand what puts these rocks and crystals together. I had fun going down wikipedia spirals around this stuff. I had no idea there were maybe 15 types of feldspars divided into 3 groups? This is going to get fun... Lol.
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fuss
spending too much on rocks
Member since October 2018
Posts: 258
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Post by fuss on Jul 6, 2020 9:07:57 GMT -5
I see Quartz(clear/grayish), Feldspar(white) and Mica (gold colored)in this pebble. Calling it granite is very reasonable, could it be a Diorite? or another igneous rock? quite possible. The best way to find out (other than sending it in to a lab) is to investigate the geology of the location it was found, are there rock outcrops of any sort nearby? or could it be a glacially deposited rock? or an escaped landscape stone?
Where did you find this? There should be a website that lists rock types/minerals for your area that might be helpful for this and future finds.
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Post by rockjunquie on Jul 6, 2020 10:58:25 GMT -5
Can't help, but those are really great pics for ID.
eta- It helps when you don't forget the most important word in your sentence- like "great".  |
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Post by rmf on Jul 12, 2020 20:06:24 GMT -5
The most obvious difference between granite and diorite is that diorite usually does not contain quartz, while granite is composed mostly of quartz. At least according to google.
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