The BGS viewer names the rocks I found down the west side of Scalloway harbour, near the UHI, as being "granofelsic psammite". Turns out that psammite is the name for a generic metamorphosed sandstone and that granofelsic refers to its form or texture. It means it has grains visible to the naked eye that are fairly uniform. Now I thought I'd found a schist because it was quite shiny!
