Flashy Feldspars

In late July, I got to visit the very first Pay-to-Dig mine in the state of Wisconsin, called Wisconsin Moonstone LLC, in company of my mom!

We joked that our rocks have terroir (a term usually used for wine, implying a unique taste imparted by the exact location where the grapes were grown) because there's something special and unusual about digging rocks out of the ground.

I like gemstones. I've purchased faceted stones, semi-precious cabochons, slabs, and rough stone. I've read about famous jewels. In all of that, its surprisingly rare to know which patch of earth a particular stone came out of. A few of the most famous gems have a provenance stretching back to the dirt (consider the Eureka Diamond), but the vast majority of fancy gems have a gap where they were lost, stolen, smuggled, sold quietly, or recut and renamed. And for any 'lesser' gems the provenance is never recorded, as they are mined by the bucket-full, shipped for finishing in parcels, sold to gem dealers in lots, and generally remixed in their journey to jewelers.
So we don't know where most gemstones come from.
But I dug these, so I know where these came from. That feels special.

Of course, once you've got a bag full of rough stone, there is still a lot of ground to cover (ha) before they become jewelry.

Moonstone or Labradorite?

As we were digging (which felt like gardening, honestly) we contemplated what we were digging for. The mine advertises moonstone, but we kept accidentally calling them labradorite. What's the difference?

Geology:
Both of these stones are varieties of a mineral called feldspar.
Feldspar is a group of minerals put together for their similarity in shape and attributes, although the exact chemical formula can change a bit. The group is subdivided into a number of subgroups, two of which are labradorite feldspar and orthoclase feldspar.
Poking around various Wikipedia articles, they appear to agree that labradorescent shiller (the flashy visual effect of labradorite) is found in labradorite feldspar, while adularescence (the hazy glow effect of moonstone) is found in orthoclase feldspar.

Gemology:
My gemstone ID textbook from the Gemological Institute of America agrees that a labradorite gemstone must be labradorite feldspar. However there are entries in the identification list for both moonstone as labradorite feldspar AND for moonstone as orthoclase feldspar. So GIA seems to think moonstone can be found in either mineral subgroup.

Retail:
In this case, the word 'moonstone' is being used as a trade name, and honestly they can call it whatever they want. Trade names are like brand names; the same way Advil is a trade name for ibuprofen. This is incredibly common in gemstones, where a gemstone from a specific place or with a particular color will get a slightly fancier name to distinguish it and help it sell. Herkimer diamonds, aurora quartz, and hawk's eye are all trade names rather than the scientific mineral name. Perhaps moonstone is just easier to sell than labradorite?

Cleaning the Rough

Obviously pulling rocks out of the ground involves a fair bit of dirt and dust. But also, the region we were digging in has some iron in the ground, resulting in pink and reddish stains that didn't scrub off. We were encouraged to give our stones a dip in Iron Out, a household cleaner designed to gently dissolve iron water stains in bathrooms and laundry machines. I hadn't ever heard of it, so I was excited to give it a try.

You can tell how much less orange everything is. Beyond that, I didn't see any other effects - no etching, no crumbling stones, no dampened color. If anything the flashes of color were now brighter with some of the iron deposit out of the way.
Neat!
So I did the whole lot.

A few stone are going to be tumbled or saved as mineral samples, but most of these are getting lined up for my slab saw. Slabbing breaks a big rough chunk down into (hopefully uniform) wafers of stone. My slab saw is essentially a heavy-duty tile saw, lubricated with mineral oil, but they exist in all sizes.

It occurred to me only after the first cut that my efforts with the Iron Out were premature. It can't penetrate into the stone, so the inside cuts were as pink/orange with iron stain as the outside had been before treatment. Rough slabs or preformed cabs will need to be retreated before final polish. Ah well.

I managed to get just one of my little slabs polished into a cabochon before I had to pack everything up to move. Here is a promise to future shiny treasures!