Very possibly, the red is bleed through from a box lids or label, I had a Tam DE razor stone streaked red on one side from the lid, looked pretty much just like that. The iron oxide content in these shales is low, under 5%. Not all iron oxide is red, maghemite for example, very prevalent in clay stones, is black/grey. But that streaking could be from iron oxide also, maybe, if that stone had a ton more of the reddish variety than typical. Don't think it would boost polishing though, the more white TOS were the finest, and blue/black WOA finer yet. The color could possibly from organic matter; shale is early on in lithification, and a lot of the prolith particulate is still present.
Saw marks on a shale stone that is used a lot with water are a significant liability, the peaks can/will dry out quickly and can degrade quickly, causing fissures. If you're going to leave them, sealing it can help. Traditional Jnat (shale) users will lap the saw marks flat. Or seal, or both.
Saw marks on a shale stone that is used a lot with water are a significant liability, the peaks can/will dry out quickly and can degrade quickly, causing fissures. If you're going to leave them, sealing it can help. Traditional Jnat (shale) users will lap the saw marks flat. Or seal, or both.
