On Apr 7, 8:01 pm, Doc wrote:
The guy at Home Depot said that if I use Liquid Nails to adhere my
window sills - which he said are some kind of composite marble, not
true marble - directly to the exposed wood frame of the window, over
time it will bleed through and become visible in the shape that it's
applied. His assertion was that I should nail lathe to the frame and
use thinset for the sills.

Thoughts?

Not exactly the same, but...

Our kitchen countertops have a fake (cast plastic) limestone "cap"
around the edges, which I originally adhered with thin-set. After
several of them fell off, I asked the pros at a local tile shop what
they would use, and it turned out to be high strength construction
adhesive.

JK