Stuff I get never has, been told it should never have an extreme smell and that aint a good sign dont know if true or not
Any noticable odour is definately not a good sign, especially considering the toxicity/cancer cancer-causing properties of the solvents and reagents commonly used in producing these drugs...some of the nastiest ones have strangely pleasant smells aswell..
Solvents should be fairly volatile though so if the material is "clumpy"/not completely dry and smells, spreading it out thinly on some flat surface and letting it air for a while in a ventilated area may get rid of any smell and some health risks.
Other contaminants are more of a problem because if the material you have is a crude precipitate from evaporation, they can become trapped in the crystal lattice, may be undetectable without professional TLC/GC-MS analysis and ultmately are destined to be ingested if you use the stuff. I've never seen a synthesis for 4-methylmethcathinone described myself, but I'll wager that none of the precursors/reagents etc involved are things you would want to be exposed to on a regular basis.
IMO a good indicator of a "better quality/potentially less hazardous" sample is uniformity of the shape and size of the crystals, which should be colourless, free-flowing/completely dry and odourless - to me that suggests recrystallisation of the crude precipitate as the final step of the production (which removes more contaminants), aswell as proper care and attention in making sure all the solvent is removed.
Another point is that during packing and transportation, crystals will probably get damaged and break up a bit, leading to finer particles which will end up settling to the bottom of whatever container the stuff is in, which could explain inconsistencies in a vendors wares especially as they reach the bottom of the container.
BTW, I fully expect someone with an actual education in this subject to come along point out that everything I've just said is total bollocks
