Unusual for boletes, A. mirabilis sometimes appears to fruit on the wood or woody debris of Hemlock trees, suggesting a saprobic lifestyle.

These similarities include the disproportionately long stipe which is frequently shaggy-reticulate and constricted at the apex, and a comparatively small pileus.

[6] Nine years later, after further consideration, Thiers changed his mind: In an earlier paper this species was considered to belong to the genus Boletellus because of its stature, general appearance, and because some workers had reported the spores as being obscurely punctate or roughened.

[13] In a 2001 analysis of ribosomal DNA sequences for a number of taxa in the Boletales order, A. mirabilis was found to be most closely related to species such as Boletus edulis, Phylloporus rhodoxanthus, and Tylopilus felleus.

[9] The bulk of Aureoboletus mirabilis is typically hidden from sight, existing as masses of almost invisible fungal threads called mycelium, which form the active feeding and growing structures of the fungus.

Young specimens may have a small flap of thin tissue attached to the margin or edge of the cap, remnants of a reduced partial veil.

[2] The tubes underneath the cap are up to 2.5 cm (1 in) long,[16] and are initially pale yellowish before becoming greenish-yellow with age, or mustard-yellow if injured.

[16] Aureoboletus mirabilis is edible, yet tasteless according to Murrill, who also noted "this is one of the most difficult species to preserve, owing to its extremely juicy consistency".

Pigments present in the fungal hyphae are dissolved or react differently with various chemicals, and the color reactions may be used as taxonomic characters.

When a drop of 10% aqueous solution of ammonium hydroxide is applied to the cap of B. mirabilis, the tissue turns a fleeting pink color that fades away.

[22] Aureoboletus mirabilis differs from other boletes in the covering of the cap, which superficially resembles that found on the surface of Boletellus ananas and Strobilomyces strobilaceus, but the scales are more rigid with a somewhat conical shape.

[21] The fungus is strongly suspected to form mycorrhizal associations with hemlock, although standard attempts at growing B. mirabilis mycorrhizae in laboratory culture have failed.

[23] Although fruit bodies are sometimes found growing on logs with advanced brown cubical rot—a trait suggestive of cellulose-decomposing saprobic fungi—the rotten wood harboring the fungi typically contains abundant conifer roots.

It has been suggested that B. mirabilis has specifically adapted to this niche to reduce competition for nutrients with other mycorrhizal fungi, and further, that the inability to culture mycorrhizae in the lab using standard techniques may be because certain physical or chemical characteristics of the wood with brown cubical rot are required for fungal growth.