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Did - this is why rocks should be called by their proper names and not some flight of fancy, marketing gimmick (even the UK from a century ago). The other trouble is does that name fit the rock - maybe the yard just liked that name (grumble, grumble).
You could try putting vinegar on it. What's tank ph?
Apart from the limestone or sandstone (depending if carbonate cement) lifting ph, those rocks should be fairly safe. I'd go for rocks that look fairly fresh and no soil on them.
If there are any sulphides like pyrite on them (I think low risk), I'd skip those rocks. Just more risk of metals like arsenic.