Funny that this simple test has been the source of a lot of consternation, much of which will have to wait for a more thorough re-telling. Suffice it to say, that my colleague, who will want to remain anonymous, and I knew the importance of finding a repeatable field test. We found out about the time of Austin passing its sealant ban, that there was no easy way to figure this out published.
After some trial and error, we have come up with a pretty reliable and definitely cheap test. The USGS successfully used this on the Indoor Dust Study (2010) to differentiate between coal tar sealed and asphalt sealed parking lots.