Description: The thallus of this crustose lichen is like dark grey compacted mud scattered with flat black, thinly edged discs. It grows on siliceous rocks in upland situations, but is not easily told in the field. It can be distinguished by a process of elimination: K- thallus, epithecium olive green, and exciple blackish at the outer edge; it contains confluentic acid which can be tested for. Lookalikes include L. lapicida (described elsewhere), which has a paler grey thallus and is K+ yellow. It is widely recorded in Ireland, though some records are very likely to be errors.

Key Identification Features:

• Thallus K-, cracked, dark grey, studded with flat black discs with thin rims blackish not greenish at outer edge; epithecium olive green
• Contains confluentic acid; on exposed siliceous rocks in the uplands.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Lecidea confluens at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Lecidea confluens at iNaturalist World Species Observations database.