Curious if anyone can tell what this is? Not sure if it's mold or if it is something else.
The yellow in the closeup is sap I believe but the black stuff almost looks like super small poppy seeds.
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To my untrained eye, it does appear to be mold. The would indicate a moisture problem. The first place I would look is bathroom exhaust fan vents, they need to exhaust outside of the house, through the roof or out the siding, not into the attic space. Next I would check for ventilation, often in the form of soffit and ridge vents, but could also be gable vents. They need to be unobstructed. If neither of these appear to be the cause, then there could be a leak in the roof.
With any moisture sources solved, the typical remedy for the mold itself is a bleach solution, being careful to not get it on your skin, clothes, or anything else that could be damaged.
without a doubt that is mold, get a simple test kit from home depot to confirm but i've spent years in attic spaces, that my friend is black mold and is no joke. Dont use bleach, it doesn't kill all the spores, you've got to use a formulated mold killing solution like this one http://www.zoro.com/microban-disinfectant-spray-plus-size-1-gal-mint-221522000/i/G2564186/?gclid=CjwKEAiA18mzBRCo1e_-y_KLpXISJACEsANGmt9Scys6sptBznKbaWGqPJMFOi2iVK4s4CeuG3S6XhoCy5_w_wcB&gclsrc=aw.ds I'ts also important to try not to disturb the mold too much or the spores will travel. ventilate outside and spray the solution with at least a couple applications. when dried you can then work to remove the mold. Be sure to use all the proper safety procedures, you DO NOT want to ingest or breathe in the fumes from the spray or the spores from the mold. the mold is likely coming from a condensation buildup along your soffet, a good trick would be to get in there and attach cut foam blocks at the top of your wall cavity up to the roof deck to seal the soffet of from the attic space, wherever cooler and warmer air mix there will be condensation. something else you can do to help is get underneath the insulation and use 3m flashing tape to tape over partition walls, electrical wires, or any other protrusions through the ceiling plane. you'll save on heating costs by creating an envelope around your living space and cut down on the air mixing in your attic. good luck!
I don't think that necessarily looks like mold, just the usual dark staining that can happen to wet wood, and is mostly harmless. In old houses you'll usually see some spots that are stained dark or black where there was a roof leak at some point in time, which was repaired, but the stain remains.
If the wood is soft - if it's easily imprinted when you push on it - it's probably rotten.
If the dark surface of the wood smudges, it could be mold.
Here's a pdf I just turned up with some more detailed info:
It's difficult to tell based only on photos. The best course of action, is to get it tested.