Open it up, see what's inside.Someone laid an egg just a bit bigger than a quarter... one that small is a common anomaly (not something to be concerned over) and not viable.... correct?
Ditto Dat!They often don't have yolks so no would not be viable.
Fairy, fart, wind, rooster eggs are usually from a tiny piece of tissue breaking loose from the reproductive tract, or an immature ova(yolk) and the body forms an egg around it. Color can be darker than 'normal' as the pigment coating released has to cover a much smaller area so is thicker. Can happen with any age layer, but more common with older layers.