Spalting is the first form of rot. If you catch it at the right time, there is no detriment to the wood, simply black lines added. Myrtle is rather hard and is a closed pore wood so it is easy to finish. It is found near the Southern Oregon/Northern California coast. They can only get down to about 20% moisture and the locals kiln dry it from there which is not good for stability. Myrtle has a bad rep for moving point of impact for this reason. I have a bunch if anyone is interested, and they are dried here in the desert.
Pete
