White beach lichen

Description:

Looking like white paint splattered over rocks lust above high tide mark, this stuff was by far the hardest, toughest lichen I have ever seen. I couldn't scratch the tiniest part of it even with small pieces of granite. All rocks at the back of the beach had some of this. Close-up view seems to show small, 3mm dark circles which resemble apothecia on 'softer' lichens.?

Habitat:

In a small, newly allocated marine nature reserve. This stuff would have been in full sun all day.

Notes:

Yet to research this stuff... see the next spotting also for a similarly tough orange version. Search Lecidella spp