sunday express

[jamiehollie]

12a a white or colourless mineral 5l
15a in celtic myths 6l
3d a latin american intrusment 7l
22d a british overseas territory 7l

Many thanks

[Lie-in King]

12a Topaz
15a Avalon
3d Marimba
22d Bermuda

It's always nice if you post the full clues, with any letters you have placed, so that people without the puzzle can more readily help - thanks! :-)