Dr. Goldsack, with a little help from Dr. Vonderhaar, has confirmed that yes, the substance is indeed a mixture of 'sum sum' and 'human presence' (what that means, only they'll know and they're not letting that cat out of the bag).
Speaking of which, I'm sorry to inform you, TBlaar, that the two practitioners in question used what would've been your prize bag to transport the substance to an undisclosed location. Please bear with us, we'll present you with some kind of solacement.
It is a thick bioplasmic excretion, left behind after the skin mold shedding of the Plecxnahr, native to the Epsilon Eridani solar system. This only happens once every 1134 years when all their planets align, which makes this high-viscosity slime a very rare and sought after commodity.