Is this chaga?

[Walkswithdog]

From the pics I would vote no but quite unsure really. It looks almost as if the surface was reflective when all the chagas I have seen are matt. Break off a piece.

That's the wet! Its been raining here heavily every day since the big bang. Everything is reflective (think of dipping a dry stone into the sea).

 

[Toddy]

I've checked a load of other birch trees in the same wood: nothing at all.

Not uncommon. Not in Scotland. We do get cold, but we don't get cold enough long enough in many areas. Think of the chaga a bit like warts....they need just the right condition to latch onto skin. Well the chaga needs just the right conditions to get a start in a birch tree.
The fomes, the Devil's Hoofnail, that just seems to get into birch anywhere they're damp.....lot of it in Scotland

M

 

[Sundowner]

I'd still dry it and drink it. Too valuable!!