(Peck) Halling & Both

Peck described this as Boletus separans in 1873. Halling & Both (1998: Bull. Buffalo Soc. Nat. Sci. 36: 239-243) transferred it to Xanthoconium on the basis of the color of the spore deposit (rusty brownish, not olivaceous), the aquamarine reaction on the pileipellis with ammonia, a strong, putrid odor developing after maturity and other features shared with other members of the genus Xanthoconium.

This species is very variable in color-from deep lilac on pileus and stipe to very pale lilac in some collections. In age the pileus tends to develop yellowish or ochraceous tones, even reddish tones. These will produce a cherry red reaction with ammonia, as does the pore surface. Indeed one can find single basidiocarps that will give both reactions: aquamarine on lilac portions, red on yellow portions!