That’s my guess- matrix, when present on magnesite, is this strange brown color. Matrix on howlite is a telltale gray. Remember when “ white Buffalo turquoise” was a thing in the market? That was ivory white magnesite with matrix.. It made a little splash for a time. The white areas where the dye “ missed” are a new thing for me. As Uncle Russ used to say....” no turquoise was harmed in the creation of these beads...”