Mesquite bowl with turquoise inlay, 9.13"

A barkless natural-edge bowl with turquoise inlay in the bottom. An interesting characteristic of this piece of mesquite is that it appears to have two heartwoods. At the very edge is just a bit of yellow sapwood. Inside that is what should (by location and coloration) be the heartwood, but inside that, at the center, is a third, lighter-colored set of rings. If anyone can explain to me what might have caused this, I’d love to know; please email me. The tree from which this piece came grew by a canal in southern Phoenix and was reported to have been 150 years old; members of our woodturning club salvaged it and a couple of other mesquite trees before developers could bulldoze them down and haul them off to the dump.