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Caloplaca arenaria (Pers.) Müll. Arg.

Granite firedot, sandwort orange lichen

KingdomFungiMushrooms, lichens, gel fungi, yeasts, and molds; also called eukaryotes
DivisionAscomycotaSac fungi
SubdivisionPezizomycotinaSac fungi with filaments
ClassLecanoromycetes“Lichenized” fungi
OrderLecanoralesMostly lichen-forming fungi
SuborderTeloschistineaeIncludes Caloplaca, Fulgensia, Teloschistes, Xanthoria, others
FamilyTeloschistaceaeIncludes Caloplaca, Teleschistes, Xanthoria
GenusCaloplacaColorful rock-growing lichens
SpeciesarenariaFrom the Latin arena, “sand,” referring to the sandy habitats of many species

About plant names...

Granite firedot lichen occurs worldwide.

Identification: This rock-dwelling lichen is so thin that it looks at first like rust on the rock. It appears most commonly on granite, but can appear on other non-calcareous rocks. Its fruiting structures (apothecia) are dark red and very small, less than a millimeter across, wide and flat, like irregular tiles, without the white powdery covering that occurs in some other lichens. This is the only rock-dwelling lichen with such a dark red appearance.

Online References:

Stephen Sharnoff Photography

The Mushroom Observer

The Stridvall Family Domain


Wisconsin Mushrooms

The Consortium of North American Lichen Herbaria

Caloplaca lamprocheila (DC.) Flagey


Caloplaca arenaria description by Thomas H. Kent, last updated 25 May 2020.

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Caloplaca arenaria (granite firedot, sandwort orange lichen)

7/30/2023 · Point Lookout, Lincolnville, Maine ID is uncertain