[Imajie]

If you have samples of both materials you could do a simple test to get an answer probably not most accurate but better than nothing.

If you have a smaller piece of one of the materials and put it towards the end of a longer piece of the other and raise that end until it begins to slide down at a constant rate. The tangent of the angle would be your coefficient of kinetic friction because at that angle the parallel force of gravity is equal to the force of kinetic friction. This paper provides a better explanation of why it is.