Re: basaltic shergottite
Certainly a volcanic vug could erupt almost anywhere. But Florida is not noted for that activity. All of the Hawaiian Islands are volcanoes, for example.
Anytime enough iron is present in a rock it will yield sparks when cut with a diamond saw. I can see visible globules in your close-ups of what looks like iron, but in tiny proportions.
I hope your assessment is correct, because even in tiny quantities your title suggests the rarest of the rare. So rare that even slabbing the material must be considered carefully.
So rare that other options must be considered as well. You may have found ballast stones from a shipwreck. While uncommon that would be quite possible in Florida, and much more probable than a basaltic shergottite.
And yet ... every square mile on earth probably has at least one or more meteorite present for every 10,000 years it has been land. Or water. There is no way of predicting what stone will land where.
That leaves looking at the stones with much more detailed equipment than I or most other people have handy.
That said, most real meteorites have fusion crusts, which I do not see on these. A fusion crust is caused by the ablation of air against a stone entering the Earth's atmosphere. Usually it is black or dark brown, sometimes even rusty-colored. It rarely is over a few millimeters thick and covers the entire rock.
Did you weigh the entire stone before slabbing? If the original was less than a pound, it adds to the possibilities of being meteoritic.
One of the foremost authorities on Martian rocks lives in Hawaii. He might agree to take a look at your stone. But most meteoritists are swamped right now (and for the next several years) with material coming from Antarctica.
Another option, but expensive, is to have a detailed chemical analysis (an assay) done on one small piece of the stone. It requires destroying the stone and reducing it to powder, but can give absolute proof of content or all elements down to hundredths of an ounce per ton of material. Cost a year or so ago was $500 for expedited analysis from a lab in Canada. Expensive. But a comparison of the elements will tell you generally whether a stone is meteoritic or not.
Unless you are well-heeled, it may be beyond the reach of most TH'ers.
.... This is about as big as they get ...
