Some buyers search for a red and black opal because they want red flashes on a dark body. Red is the least common color flash in opal, and not every black opal shows it. The colors you see depend on the stone itself, so each opal is a little different.
A pendant is where many buyers want to use a stone like this. When the opal hangs free, the light reaches it from every side, and a plain chain keeps all the attention on the stone. People who look up Ethiopian black opal necklace significance often plan to give a pendant to someone who matters to them. A dark stone is also easy to wear. It goes with black, white, denim and almost every other color, so one piece can work for many outfits.