I forget learning about this, so does anyone know the answer to this?

Which sentence orders adjectives correctly?

a
The old, purple, square, shiny gem shone in the ring.

b
The purple, old, shiny, square gem shone in the ring.

c
The shiny, square, purple, old gem shone in the ring.

d
The square, shiny, old, purple gem shone in the ring.