Keystone vs. Limestone — What's the Difference?

(Architecture) A wedge-shaped stone at the top of an arch, often larger or more ornamented than the other voussoirs. Also called headstone.

Limestone is a common type of carbonate sedimentary rock. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3).

The central supporting element of a whole.

A common sedimentary rock consisting mostly of calcium carbonate, CaCO3, used as a building stone and in the manufacture of lime, carbon dioxide, and cement.

(architecture) The top stone of an arch.

An abundant rock of marine and fresh-water sediments; primarily composed of calcite (CaCO₃); it occurs in a variety of forms, both crystalline and amorphous.

Something on which other things depend for support.

Pertaining to or made of limestone.

A native or resident of the American state of Pennsylvania.

A rock consisting chiefly of calcium carbonate or carbonate of lime. It sometimes contains also magnesium carbonate, and is then called magnesian or dolomitic limestone. Crystalline limestone is called marble.

(retail) A retail price that is double the cost price; a markup of 100%.

A sedimentary rock consisting mainly of calcium that was deposited by the remains of marine animals

(baseball) The combination of the shortstop and second baseman.

(transitive) To distort (an image) by projecting it onto a surface at an angle, which for example causes a square to look like a trapezoid.

To double the cost price in order to determine the retail price; to apply a markup of 100%.

The central or topmost stone of an arch. This in some styles is made different in size from the other voussoirs, or projects, or is decorated with carving. See Illust. of Arch.

A central cohesive source of support and stability;

The central building block at the top of an arch or vault