Vocabulary

Dear teachers,

I'm not sure about the usage of the word treasure with or without an article.

Context: Mary found a golden coin and tells her friend about it.

Is it possible to say:

a) My brother always looks for treasure, too, but...

or do I need to put in an article:

b) My brother always looks for a treasure, too, but...

Maybe both is possible? My dictionary refuses to help me there...

Thanks in advance