It's impossible to say as the texture and density aren't consistent. It's impossible to eyeball anything as small as 1 mg without a huge degree of variance. Your best bet would be to get a cheap scale and measure out a few hundred milligrams and dissolve this is PG or EtOH. Unless you have a fairly nice scale, you won't be able to dose with any meaningful accuracy otherwise.
You have to get a scale, 1mg of powder can vary a huge amount depending on everything from how finely it's ground to whether it's been handled to the lens of the camera used to take the picture....