LARGE CLAM SHELL W CRUSTY WEATHERED OUTSIDE BEACH HOUSE DECOR in color gradation

Description

came from a local auction.  When I saw this is  was so unique & cool, I had to have it.  I don't know if it is a clam shell or something else.  The outside is weathered, crusty and rough, like the ocean tossed  it around a bit.  The inside is almost granite like, with color gradations.  measures 8"w, 6 1/2"h, 3" deep. weighs almost 2 1/2 pounds.  (miss my days living on west coast of FL),  great seaside collectible, for beach house, or mantel decor.
note: cr ls r1