Green / White Shell from Vietnam, Imperial Turban shell.

Turbo imperialis is a species of sea snail, a marine gastropod mollusk in the family Turbinidae, the turban snails. The length of the shell varies between 50 mm and 120 mm. The large, solid shell has a globose-conic shape. It is ventricose and imperforate. Its color is green, irregularly mottled and spirally striped with chestnut, closely irregularly striate with the same color. The 6-7 convex whorls show well marked sutures, and numerous more or less conspicuous revolving furrows. The large body whorl is somewhat flattened above. The aperture is subcircular and pearly white within The outer lip is rather thin. The arched columella has a pearly callus, which reappears at the posterior angle. The green parietal wall is nearly devoid of callus. The base of the shell is slightly dilated and scarcely produced.

The shell (or snails also known as "snail") is one of limestone (calcite and / or aragonite) and other minerals existing (mostly) external skeleton, which is made by a mollusk (tribe of Mollusca). The shell gives the animal strength and protects the animal against external influences such as predation, injuries, dehydration, etc. The shell grows during the life of the mollusk. The science that studies all aspects of mollusks, called malacology. A branch of the malacology which only deals with the shell is called conchology. Previously it was considered wrong to state that malacology was not involved with the shell and the distinction between malacology and conchology was made by some very sharp. In current practice, the terms are often interchangeably, and they are more or less considered as synonyms. Shells can be used for the hardening of a passageway, which is then sometimes called a "shell path" is mentioned. Also, shells can be burned to lime shell, which is often used as a building material in the past, was used instead of cement.

 
Shells from Cebu.