About a month ago, I had 10 yards of 1 5/8" gravel delivered so I could add some more along the shoulders of my asphalt driveway. Today, I started to lay a little down to see how much work I'll have in the near future. As I shoveled some into my wheelbarrow, a glint came from the rocks. A fair portion of the rock is heavily embedded with pyrite. Should I be concerned with pyrite oxidizing and releasing sulfates as it breaks down?

I don't think it's going to weather fast enough to cause any problems in your use.

The main thing to worry about is the neighborhood kids stealing all of it because it has "gold" in it.

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Originally posted by arfmel:
I don't think it's going to weather fast enough to cause any problems in your use.

The main thing to worry about is the neighborhood kids stealing all of it because it has "gold" in it.

That's pretty much what I figured. Looks like I'll just have a sparkly driveway. No kids in the neighborhood, so I don't need to worry about it gradually disappearing.

Hard to tell from your pic; are you sure it’s pyrite, and not schist? Schist has a lot of flat grained inclusions of things like quartz and mica that catch and reflect the light as you describe. Pyrite will tarnish when exposed to weathering and become less shiny over time. Are the “shiny” spots flat, or do they appear nodular.

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Originally posted by gearhounds:
Hard to tell from your pic; are you sure it’s pyrite, and not schist? Schist has a lot of flat grained inclusions of things like quartz and mica that catch and reflect the light as you describe. Pyrite will tarnish when exposed to weathering and become less shiny over time. Are the “shiny” spots flat, or do they appear nodular.

You sure your alias shouldn't be Rockhound?

The mica in schist can be a tabular mineral and will weather more rapidly than pyrite, quartz, or feldspar, but I doubt fast enough to make a meaningful difference when used as the OP intends.

quote:

Originally posted by arfmel:
The mica in schist can be a tabular mineral and will weather more rapidly than pyrite, quartz, or feldspar, but I doubt fast enough to make a meaningful difference when used as the OP intends.

I think he was more concerned about the creation of sulfates (or kids carrying it off like dwarves) than from iron oxidation than just weathering of his gravel lol. Either way, I’m sure his yard and stability of his driveway will be fine.

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Originally posted by Georgeair:

quote:

Originally posted by gearhounds:
Hard to tell from your pic; are you sure it’s pyrite, and not schist? Schist has a lot of flat grained inclusions of things like quartz and mica that catch and reflect the light as you describe. Pyrite will tarnish when exposed to weathering and become less shiny over time. Are the “shiny” spots flat, or do they appear nodular.

You sure your alias shouldn't be Rockhound?

Lol

quote:

Originally posted by gearhounds:
Hard to tell from your pic; are you sure it’s pyrite, and not schist? Schist has a lot of flat grained inclusions of things like quartz and mica that catch and reflect the light as you describe. Pyrite will tarnish when exposed to weathering and become less shiny over time. Are the “shiny” spots flat, or do they appear nodular.

They look flat. I don't think it will be a problem using the rock along my driveway.

quote:

Originally posted by gearhounds:

quote:

Originally posted by arfmel:
The mica in schist can be a tabular mineral and will weather more rapidly than pyrite, quartz, or feldspar, but I doubt fast enough to make a meaningful difference when used as the OP intends.

I think he was more concerned about the creation of sulfates (or kids carrying it off like dwarves) than from iron oxidation than just weathering of his gravel lol. Either way, I’m sure his yard and stability of his driveway will be fine.

Any suffates created would be the result of weathering.

quote:

Originally posted by arfmel:

quote:

Originally posted by gearhounds:

quote:

Originally posted by arfmel:
The mica in schist can be a tabular mineral and will weather more rapidly than pyrite, quartz, or feldspar, but I doubt fast enough to make a meaningful difference when used as the OP intends.

I think he was more concerned about the creation of sulfates (or kids carrying it off like dwarves) than from iron oxidation than just weathering of his gravel lol. Either way, I’m sure his yard and stability of his driveway will be fine.

Any suffates created would be the result of weathering.

Yes, but mica breaking down does not produce them. Iron based minerals do. If his gravel has mica or quartz inclusions, it is not a concern. I think you may have misunderstood my point.

quote:

Originally posted by gearhounds:

quote:

Originally posted by arfmel:

quote:

Originally posted by gearhounds:

quote:

Originally posted by arfmel:
The mica in schist can be a tabular mineral and will weather more rapidly than pyrite, quartz, or feldspar, but I doubt fast enough to make a meaningful difference when used as the OP intends.

I think he was more concerned about the creation of sulfates (or kids carrying it off like dwarves) than from iron oxidation than just weathering of his gravel lol. Either way, I’m sure his yard and stability of his driveway will be fine.

Any suffates created would be the result of weathering.

Yes, but mica breaking down does not produce them. Iron based minerals do. If his gravel has mica or quartz inclusions, it is not a concern. I think you may have misunderstood my point.

Right.

The picture looks to me like something that came from igneous rock or slag from a smelter.