I live in Hawaii and help identity wood species at a materials recycling business. It looks like the right grain patterns for Koa. The color is so shifted in the photo that you can't identify from it. It is not a heavy wood and describing it as similar to walnut sounds right.I wanted to make some pens out of Hawaiian koa wood, so I bought a few blanks off ebay. I've never worked with Koa before, but the blanks seemed unusually lightweight. I read online that it's a medium density wood similar to walnut, but I can tell very easily that they are not the same weight. Here's a picture of the blanks:
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So do you guys think this is really Koa?