wut is this?

[stdenis_jd]

Hi everybody, new guy here...wondering if anyone can tell me what this rock is...fairly dense, I'm thinking possibly Jasper but it's a little too rough to be Jasper or Flint. I do a lot of rock-hounding in northern lower peninsula Michigan (US) and I found it in a gravel pit. Any ideas?

 

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[EricTheCat]

It has the exact same color as a lot of iron-rich jasper I find in my area but the texture does seem a bit on the rough side. Does it have a waxy luster and are there any broken areas on it where you can see a conchoidal fracture? A hardness test might help limit the possibilities but if it has the luster and conchoidal fracture (hard to tell from the picture) it's a definite maybe.

By the way, welcome aboard!

 

[stdenis_jd]

Thx for the reply and the welcome Eric!

I'm not sure if they would be conchoidal fractures, they don't appear to be similar to how a quartz crystal or obsidian would break, but there are several flat surfaces on it. It is a little rough on the top (in the photo) but the bottom does have some smooth surfaces. The vertical white line you can see to the right is a quartz vein if that helps. On the flat/smooth surfaces it does have a slightly waxy luster though.

I'm leaning further toward it being red Jasper now. Can't imagine what else it could be. It's harder than 440 stainless steel (my pocket knife) but I scratched it on one of my pudding stones (white quartz sand matrix) and it streaked red against the white so it appears to be slightly less hard than semi-pure quartz.

 

[DDancer]

That looks to be pretty close to a jasper but the crystal grains seem to be to large so it kinda falls in the grab bag of a quartzite. With that scratch test its high in iron so I'm guessing its more hematite than quartz. My thoughts.

 

[stdenis_jd]

Thx DDancer yeah a high metal/quartz ratio would explain the appearance of Jasper, but softer and slightly different structure. I'm thinking you're right about it not really fitting the bill for a Jasper and being more of a quartzite.thx for the insight!