I have access to all the roadbed building materials around here that the railroads had. So line, I bought a classifier and am making my own ballast/groundcover. The only track that gets a purchased product is the GN mainline on the freight. The biggest use of material for the RRs when they started building was red cinders. Complete "buttes" were obliterated for roadbed/fill. Most of my non-mainline tracks will have ballast of red cinder, but there are other places I will use other types of rock.
Six different size mesh screens in this one...... The 35 size I'm using on the shoulders of the track and 60 between the rails in the cribs.
And of course, all sizes can be used for landscaping.... It has been a while since I got these, I believe the meshes come in different combinations....
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All of these are #10.....
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From left to right..........
I call this one Lower Lake, because that is where I got it. It is a grey, finer grain sand, no material stayed in the #5 mesh......
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Black cinder....not as plentiful as red cinder, but lots of it none the same......
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Pumice...pure volcanic pumice... Not so much for roadbeds, I was thinking loads, other stuff.......
(Pumice is volcanic glass--obsidian--frothed up like a milkshake......)
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This one is called Perez, because it came from the area around the Perez siding on the Modoc Northern track of the UP.
I like the color of this so I'm using it as a major source of ground cover. It's probably a little more reddish than the picture shows.....
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I did give both the red & black cinders a magnet test. I have a little extendable parts magnet that I poked in the cinder. Yep, they are magnetic. I ballasted a section of track in both the red & black cinders, and after thoroughly drying & cleaned up, retested with magnet, and of course nothing stuck because it was glued down, but if there is a question on the cinder being magnetic and a loco(s) running over it and something happening? idk. I will find out! I am going with it.....
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I would offer red cinder (rocks) to anyone that would like some, no charge, you pay shipping.......
Happy Modeling!