It can be field tested immediately close enough
Toss a pinch in the vial solution and stick the strip in
Plus any cop knows if it smells like coke
Heroin has little smell
Field tests are somewhat unreliable and are not admissible in most states for evidentiary purposes. Lab results are required to prove the chemical composition of an item. Until lab results are obtained the proper documentation on an inventory is green leafy substance or white powder.