The lichen thallus has an uneven and scaly texture, forming patches up to 40 mm wide in dull greenish-grey or brownish-grey.

The type specimen was collected by the author in 2013 at Creek Bay Farm on Kangaroo Island, at an elevation of 85 m (279 ft).

The species name honours the Ukrainian lichenologist Sergey Kondratyuk, "in acknowledgement of his enormous contributions to the taxonomy of the genus Caloplaca in Australia".

[1] The apothecia of Eilifdahlia sergeyana, the lichen's fruiting bodies, are scattered and range in colour from orange to orange-yellow.

[1] Beneath the apothecia, the subhymenium is mostly hyaline (translucent) with a yellowish band at the lower part, measuring 30–40 μm thick.

The hymenium above is 70–80 μm thick, also hyaline and not inspersed with oil droplets, and covered by a dense band of golden-yellow crystals similar to the apothecial margin.

[5] Eilifdahlia sergeyana is known to occur only at the type locality on the Dudley Peninsula of Kangaroo Island, where it grows on sandstone boulders.