okay will try again this time in point form
1. Ebony is a kind of wood. If the gloves are ebony it would mean that eartbenders are also able to bend wood and (presumably) other organic materials
2. Onyx is a kind of stone, but onyx has white stripes so the gloves can be onyx. The can however be black jasper. onyx and jasper are mebers of the same mineral family??and are both made of of billions of tiny interlocked quartz crystals??(in onys these are in layers in jasper they aren't) Jasper would be a likely choice as it is very tough and durable. HOWEVER?? since flint is also a kind of jasper one would not want to use it in the presence of a firebender, since hitting the jasper on any hard surface (particularly metal) would create sparks which a firebender could presumably bend. (my personal glove guess is basalt)??
Final question since gunpoweder is made of ground of minerals shoundn't earthbenders be able to bend it?