It looks like an agate type of rock to me.
We already know jasper one of the agate family is good as a hone, so I would expect this to be in the same ball park if that is the case.
I'd have to be dubious about the garnets. They can form in agates, but so can a lot of other inclusions. Without an actual appraisal I'd be tempted just to have them referred to as micro crystal inclusions.
Also if it is agate you can get it for far far less, allbeit with a bit off risk of getting a dud.
Searching ebay for "large agate slice" will give you a whole heap of items.
770G Large Natural Agate Slice Geode Polished Crystal Quartz | eBay
5 mins with a tile saw and you have a hone.
What I really want to see is a video from someone I trust using it. Lynn or GSsixgun. If I see them use one and give a fair appraisal then I'd be a lot less sceptical.