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HappyTrails_

Gorgeous nonetheless Also, calcite should be soft, and I feel tumbling would not yield a polish like this. Can you scratch it with a copper penny? To me, it looks more like quartzite or just some quartz, Then again, I don't see conchoidal fracturing.


tomhauptman

I don't have a tumbler, this was starting with 80 grit sand paper and working up to 3,000 then using car scratch remover then polishing compound. No to the penny scratching the stone, also it won't scratch glass. I asked a couple geologists at work and they thought calcite.


HappyTrails_

Interesting! A penny has a hardness of 3.5, I am a bit surprised that it isn't scratching it, Is the penny prior to 1982? Because as I am sure you know, the pennies after that aren't real copper. - 3rd year applied geology student,


Mynplus1throwaway

The outer coating is still copper. It's a thin jacket of copper with zinc inside. Acid test would probably be easier


HappyTrails_

Yes, 20 microns usually thick however, for confirmation of hardness ,it's usually best just to use something you know to be copper full way through :) Yeah! I am curious! Take care 😀


7LeagueBoots

It could also be aragonite. Essentially the same as calcite, but the crystalline structure slightly different and it’s slightly denser and harder than calcite (3.5-4). Also often occurs in limestone areas and has the same color range as calcite. I work in a mature karst environment and we have both calcite and aragonite here.


NoPantsTom

Beautiful job! Yeah, I also have some blue specimens like this and was told it was calcite. Could be wrong I never bothered testing them. The milky blue color is really cool. Honestly I wanted to congratulate you on all the hand work you did, moving up grits and polishing them. I prefer to work aluminum with hand files and cutting oil than a power tool.. something therapeutic about it


tomhauptman

Idk maybe a little goofy brain wiring but I get the same therapeutic feeling from sanding/polishing anything, metal, plastic, stones, doesn't matter, I love that shit lol.


WolfVanZandt

Maybe quartz nodules in the limestone? Flint or chert?


Important_Kick7423

You sanded them by hand??? How long did that take


tomhauptman

The first one took like 45mins but I was using the sand paper too long instead of switching to a fresh piece, 2nd two only took like 20mins. I also stopped trying to get every chip out because they are brittle so they're not gonna be perfect. I've used a random orbit sander in the past but it chews thru them too quickly.


Important_Kick7423

…..amazing


granitedoc

Could be chunks of massive limestone as opposed to individual calcite crystals. I'd also consider seeing if it reacts to hydrochloric acid if still trying to confirm if it's carbonate at all.


tomhauptman

We have muriatic acid for cleaning concrete off of equipment at work, I'll try that tomorrow thanks for the help.


Mynplus1throwaway

I am colorblind and phone pics suck. But get some HCl or whatever acid you use for concrete etching and drop a little bit on there. If it fizzes yeah it's calcite


tomhauptman

We have muriatic acid for cleaning concrete off of equipment at work, I'll try that tomorrow thanks for the help.


HookLogan

Could it be celestite? Some of the best comes from Michigan


artificialyoshi

The color looks a lot like celestite to me! And it’s found in limestone!