Shell marble

Marble \Mar"ble\ (m[aum]r"b'l), n. [OE. marbel, marbre, F.
   marbre, L. marmor, fr. Gr. ma`rmaros, fr. marmai`rein to
   sparkle, flash. Cf. {Marmoreal}.]
   1. A massive, compact limestone; a variety of calcite,
      capable of being polished and used for architectural and
      ornamental purposes. The color varies from white to black,
      being sometimes yellow, red, and green, and frequently
      beautifully veined or clouded. The name is also given to
      other rocks of like use and appearance, as serpentine or
      verd antique marble, and less properly to polished
      porphyry, granite, etc.
      [1913 Webster]

   Note:

   {Breccia marble} consists of limestone fragments cemented
      together.

   {Ruin marble}, when polished, shows forms resembling ruins,
      due to disseminated iron oxide.

   {Shell marble} contains fossil shells.

   {Statuary marble} is a pure, white, fine-grained kind,
      including Parian (from Paros) and Carrara marble. If
      coarsely granular it is called saccharoidal.
      [1913 Webster]

   2. A thing made of, or resembling, marble, as a work of art,
      or record, in marble; or, in the plural, a collection of
      such works; as, the Arundel or Arundelian marbles; the
      Elgin marbles.
      [1913 Webster]

   3. A little ball of glass, marble, porcelain, or of some
      other hard substance, used as a plaything by children; or,
      in the plural, a child's game played with marbles.
      [1913 Webster]

   Note: Marble is also much used in self-explaining compounds;
         when used figuratively in compounds it commonly means,
         hard, cold, destitute of compassion or feeling; as,
         marble-breasted, marble-faced, marble-hearted.
         [1913 Webster]