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A general guide for using the Forum with some rules and tips
Rock identification help :)
  
  Index -> FOR BEGINNERS: What is it? Where is it from?
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McCallBecker




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PostPosted: Nov 18, 2018 23:27    Post subject: Rock identification help :)  

Hello! I was wondering if anyone could help me identify this type of rock!!? I live in California. I find these when hiking in the hills. There are dirt trails in the hills that someone made that are a bit gravel-y and these rocks are on the trails. These rocks are very smooth and feel calming to touch. They're a nice dark black. I'm able to scratch stainless steel with them so they're pretty hard. I was wondering if anyone knew what they were!? I was trying to find out on my own through searching the internet but I'm lost. My conclusion was Basalt, but I don't think that's right. I would love if someone could help me out. Thank you!!!


IMG_7433.jpg
 Mineral: I'm not sure, was wondering if someone could tell me
 Dimensions: 1-3cm +
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Jordi Fabre
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PostPosted: Nov 19, 2018 02:41    Post subject: Re: Rock identification help :)  

SteveB wrote:

Can you run some more tests (there is a sticky thread here on identifying specimens with info). On first glance they could be basalt. I’m guessing though they are black river pebbles readily available at hardware stores for gardens and paths, rather than naturally formed in place where you found them as you said its a man made path. At this point I dont think location could be determined or where you found them helpful in further identification. A visit to a local landscaping supplier may be able to provide guidance to local sources of such pebbles.

They are likely volcanic in origin and have been worn and tumbled smooth by the long action of moving water with silts. If they are natural to the location you should be able to find them in cuts in the uphill slopes usually made to provide a “wall/cliff” edge to paths, you may then also find conglomerates containing these pebbles and other stones. Natural conglomerates can be very interesting and colourful with the diversity of stones that are included.

I’d suggest the comfort you felt holding them is due to the smoothness along with a warmth since stones are thought to be cold and often are. Rounded pebbles are less often encountered. Plus being black they absorb radiant heat from the sun and retain it so they tend to be warm to the touch too even when encountered in shaded areas.



Thanks Steve, the anti spam stopped your post due the words "path.At" (without space) that the anti spam system detected as a web page.
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SteveB




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PostPosted: Nov 19, 2018 10:12    Post subject: Re: Rock identification help :)  

Thanks for good moderating. Sorry ill try to be more vigilant in my typing on ipad.

For original poster:

Read the post here http://www.mineral-forum.com/message-board/viewtopic.php?p=19487#19487

This will help you run simple tests to help identify the specimens. If they are from landscaping supplies they may not know what type of mineral it is. I have sime bags of stones for my garden and there is no indication of what type of stones they are. They are basically all the same rough shape size and colour and appear to be mostly the same mineral there are odd ones that are similar in visual appearance. They are cheap and for decoration in a garden so are not professionally identified. But atill they yours may have come from a lical quarry which can be researched at your local library usually and find accurate answers. If these stones are not landscaping but natural to where you found them see if there are conglomerates too in the area and the landscape may hold hints to their source further upgill or upstream.
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McCallBecker




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PostPosted: Nov 19, 2018 12:53    Post subject: Re: Rock identification help :)  

Thank you so much for that response Steve! I really do appreciating you taking your time to write all of that for me!! I'm going to go back and check the hill slopes or any cliffs/walls I can find out there and see if there's anything and look for the conglomerates as well. You're right they could have been brought there when the path was made, but I've also found these same rocks on trails out in other hills around my area (like towns away). I live in a valley so I feel like they could be natural if the whole area was once under water. ? That's just my thinking. The other area where I found these types of rocks does in fact have clam shells and other fossils embedded in rocks, and this is way up when climbing up a huge hill! So that made me think they're some kind of river/creek stone. Thank you for providing that link for me to do more testing. And again thank you for all of that helpful information!! I do appreciate it. I'll make sure to post if I find anything out! :)
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SteveB




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PostPosted: Nov 19, 2018 14:43    Post subject: Re: Rock identification help :)  

Wow, I’m so jealous. I love fossicking and fossils have been so rare for me to find, just never lived where there was easy above ground finds. It could be the stones are entirely native to the area and if you find say natural gullies or exposed ground from land slides or large fallen trees which show the stones are in the sub layers are good signs if you are lucky there may be areas where the ground has been cut into like a slice, usually along a road, where strata layers can be seen and you may even spot a black layer of pebbles that could indicate an ancient beach where they were formed over long time. But you may find more smaller pockets of them with undulating land folds that might be more akin to ancient riverbeds. Clam fossils would indicate more marine than river. It takes a long time to smoothly round pebbles and the breaking of waves on a sea/ocean edge beach is most likely though not certain. I think some enquiries at the local library on the geology of the area will offer more information. Like with panning for gold or gemstones the constant action of waves results in softer/lighter minerals being broken down and carried away, these black stones would all end up together being the same size and density. There may be other pockets of different similar pebbles of different densities nearby too. Its a good way to get a better understanding of the area you live in and can maybe find groups you could join to explore and discover with. So many of us live in urban or farmland areas where the top few feet of the ground has been bulldozed and turned/paved so we dont get the experience of exploring the natural geology and while large colourful mineral specimens are rare at the surface due to weathering the presence of smaller specimenscan indicate the possibility of spectacular ones safely protected in the dirt just under your feet which is why after a large storm you can go out and find fresh landslides and fallen trees which expose whats inside the ground and if you’re lucky find nice specimens.
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Pete Modreski
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PostPosted: Nov 19, 2018 14:53    Post subject: Re: Rock identification help :)  

Dear McCall,
Notwithstanding the good advice about reading the page(s) on our Forum site about simple tests that may help identify a stone--in all likelihood, since your pebbles are just "rock" pebbles and not crystallized minerals, you are probably not going to find much in the way of identity tests that will really help you.

In fact, identifying the exact nature of rocks or stones like you have--smooth, black or near-black, fine-grained pebbles--can be a really difficult, to "well-nigh impossible" challenge, even for an experienced geologist. There are just so many types of fine-grained, dark rocks that all can look so very similar, that there is just not much to go on, to lead to a sure identification. It, of course, "can" be done, but it might take some professional, expensive equipment to do so--the kind of thing that a university or other laboratory could do--but only if they had some compelling reason to really need to know that!

If I list some of the possible types of rock that this could be, my best advice to you is to look up, online, information about what all these types of rocks are--and what the differences between them are--and try to make your own best judgements. But, keeping in mind, you really may not be able to tell, with any certainty! Also to keep in mind; the stones MAY be of local origin, but for all you know, they could be something that is imported in large quantities from, who knows where--China, India, Brazil--it's very cheap to bring in rock material by the ship-load, often because the actual cost of mining the rock is so much cheaper in other countries than here in the U.S., that the cost of transportation is minor compared to it.

So, back to possible rock types. And, though I will list "basalt" first (as per your own suggestion), I think it's more likely that these may be one of the diverse kinds of fine-grained, slightly metamorphosed sedimentary rocks that I'll list last. And another thing to keep in mind, these types of rocks are not necessarily "distinct"--like species of plants or animals have to be--but they can all be gradational; hence, the specimens you see may be intermediate, transitional varieties between these kinds of rocks that I may list. Some possibilities, for near-black, fine-grained rocks:

Basalt (igneous rock)
Chert or jasper (types of hard, fine-grained silica (quartz), colored by impurities)
Sedimentary rocks: limestone, siltstone [these would both be softer, so, probably not what you have]
Slightly metamorphosed sedimentary rocks:
Meta-siltstone
Meta-chert
Argillite or meta-argillite
Slate
Greenstone (metamorphosed basalt)
Quartzite

Best of luck to you!
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McCallBecker




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PostPosted: Nov 19, 2018 20:45    Post subject: Re: Rock identification help :)  

Steve, thank you for all of that wonderful insight! I'm a total novice of rock information but you've given me some stuff to consider. I love rocks though and can spend all day looking at the dirt lol, so I appreciate the ideas you've given me. There are actually often a lot of gullies in the hills where I live as well as those roads you spoke of that cut into the ground. So those would be fun to inspect, especially after a rainfall as you say. About the fossils, they're really only on big rocks to inspect. I don't think there's any fossils to claim easily, as far as I know. But they're definitely cool to look at. I just tried to attach a picture of a clam fossil at the top of a huge hill in my area but for some reason it's not letting me attach the file to this comment.. :p
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McCallBecker




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PostPosted: Nov 19, 2018 20:51    Post subject: Re: Rock identification help :)  

Pete, thank you for that information! I was definitely wondering if it would be possible at all for me to identify the rock! lol. I just find these smooth little black rocks so magical and so I was hoping to be able to find out what they were, as I like looking up the spiritual and metaphysical meanings behind types of rocks and crystals! Thank you for the insight and for including a list of what you think they could be for me to check out. I super appreciate it!! :)
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