Very little reliable to distinguish them - a lot of botanists don't recognise it as distinct at all. Tends to be greener, less glaucous, but that isn't wholly reliable.

Resin

Black Hills Spruce is a regional variation of White Spruce (Picea glauca). Commercially available Black Hills Spruce are nothing more than seedlings grown from forms with better blue color than traditional P. glauca. I have seen large nursery blocks of trees labeled as Black Hills with substantial variation....from trees that were indistinguishable from regular P. glauca to trees that are so blue they rival the best grafted Colorado Blue Spruce.