When you first see the weed be sure to have a good look at it, preferably in bright natural light. Be aware of the various types of contaminant.
The first type of contamination to be noticed was grit weed, this stuff was covered in tiny glass like particles, found to be silica. It’s not around much now, but its worthwhile knowing how to test for the dreaded grit weed. If you use one of the metal herb grinders you may notice unusual screeching or scraping, the grit may even leave marks on your grinder. If you suspect its grit weed don’t put it near your mouth to test for a crunch instead give it shake over a surface you don’t mind being scrapped like a blank cd. Then roll a glass over whatever crystal has fallen onto the cd. Listen carefully and if you hear crunching you know its grit weed.
One of the best ways to test is to look at the stems, scrape the stem with your nail and see if anything flakes off , if it does then you know its been coated with some type of substance. Theres not much crystal on the stems if any so when it looks like there is its an obvious giveaway that its been adulterated, you may see fine hairs which is normal.
You may come across weed that when burnt the ash becomes hard, flicking the ash may result in the head of your joint falling off. Rubbing this hard ash on fingers leaves a black oily residue not associated with clean cannabis or tobacco.
Sweet bud, sugar bud, sugar weed whatever you want to call it will smell similar to candy floss when burnt and will be sweet to taste with your tounge( I don’t recommend putting anything near your mouth if you don’t know where its come from).
I doubt that I have covered all forms of contamination in this article, if you know of any other tests, tips or even pictures please make contact.