Collection location: Vista House, Multnomah Co., Oregon, USA [Click for map]
Greenish to yellowish crustose lichen found growing on basalt railings and stonework at Vista House.
[admin – Sat Aug 14 02:07:20 +0000 2010]: Changed location name from ‘Vista House, Multnomah County, Oregon’ to ‘Vista House, Multnomah Co., Oregon, USA’
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There are several other granular crustose lichens of the same color. Generally I can make out a few intact lobes in your photo, strongly suggesting Candelaria (even that can be an incorrect deduction), but the one in this photo look purely powdery. Other possibilities are: Chrysothrix (purely powdery or “leprose”), Candelariella efflorescens (only bark, so we can rule it out for this specimen), and Caloplaca (reacts K+ red and is typically oranger).