Answer:
I usually wear a yellow coat. I usually have a dark head. I make marks wherever I go.
In the night a mountain, in the morning a meadow.
Thousands lay up gold within this house. But no man made it. Spears past counting guard this house, but no man wards it.
Vikings use this for warmth.
I can be short and sometimes hot. When displayed, I rarely impress.
What is so fragile that saying its name breaks it?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?