Diamond grid, hard work gone into this. Well done.
Good all round general knowledge.
Phew !!! 24 seconds left on the clock.
10s all round.
Thanks for posting.

It was good but for some reason one square in every category is incredibly obscure. A waxy substance found in whale's intestines? An obsuce mineral corundum? Mineraloids that are the lowest rank of coal? A song that reached number 9 in the 1970's? One of these was in every category and I'm all up for a challenge but it was so out of touch with the rest of the grid. It's not for me but if other people like it then fair play. I would look for more consistency with the level within the grid myself. Thanks for posting.

I failed at this, sorted two lines, saw three links. Couldn't get past coal for lignite, and tried everything but xxxv as the fourth in the other line. Really good.

Only 3/10, but thanks for the detailed explanations.