Steve, I just read this post and you got my curiosity up.
I lent out my Oxalic Acid crystals to a bee buddy, so I could not use the actual crystals themselves for measuring.
But, if brown sugar has the approximate same weight, this is what I came up with.
1/2 teaspoon of UNPACKED brown sugar = 2.5 grams
I have a digital scale that measures up to 150 grams and it is very accurate. So, presuming that both are the same weight and density, this is what the scale showed. Hope that helped a bit. Have a great and wonderful day, Cindi