BRIEF DESCRIPTION: The following is largely based on the original description of Miller (1992).

The cap of Amanita griseibrunnea is 30 - 65 (-83) mm wide, broadly convex to plane in age, orange-gray, darkening to brownish-gray, with a nonstriate and appendiculate margin.  The volval remnants are present as white, mealy, slightly sticky volva, usually embedded with sand grains, and wearing away with age.  The flesh is white, firm, and unchanging when bruised.

The gills are close, medium broad, narrowly adnate, white; short gills are present in at least one tier.

The stem is 60 - 130 × 11 - 23 mm, flaring somewhat at the top, otherwise cylindric, white, with a mealy-fibrillose powdery covering and irregular cottony patches of volva on the upper bulb.  The bulb is narrow and short, sometimes rooting and usually covered with sand.  The ring is in the upper part of the stem, white, cottony, mostly pressed to the surface of the stem forming an irregular zone, disappearing in older specimens.  Before the ring separates from the cap margin, it forms a white, submembranous layer with soft, white scales arranged like spokes of a wheel on the bottom side.  The flesh is white, firm, and unchanging when bruised.

In young material, there is a faint odor of chlorine that becomes disagreeable in age.

The spores measure (9.0-) 10 - 14 × 5 - 6 (-7) µm and are elongate to cylindric and amyloid.  Miller observes that the amyloid reaction was unusually purple.  Clamps are absent at base of basidia.

Amanita griseibrunnea was described from the state of West Australia.  This species occurs in sandy soil under Eucalyptus marginata and a European imported pine (Pinus pinaster).  While the pine was nearby, the present species was always found close to or in the root zone of Eucalyptus.