The short answer is yes. It could become a factor especially in epoxy deep pours. WATCH THIS QUICK VIDEO TO SEE THE DIFFERENCE Typical pigments average 10-60um. Be aware that larger micron sized pigments will most likely have a heavier density which will cause the pigment to sink faster in fresh epoxy such as deep pours. For example, our Icicle or 14k Nugget Gold is 200-700um and will most likely sink in fresh epoxy faster.  To alleviate sinking either let the epoxy settle up a little bit. Or, come back through your project to "stir" it a little more.