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A plane figure having four sides and angles; a quadrangle, as a square, a rhombus, etc.

Of or pertaining to a tetragon; having four angles or sides; thus, the square, the parallelogram, the rhombus, and the trapezium are tetragonal fingers.

Native tin dioxide; tin stone; a mineral occurring in tetragonal crystals of reddish brown color, and brilliant adamantine luster; also massive, sometimes in compact forms with concentric fibrous structure resembling wood (wood tin), also in rolled fragments or pebbly (Stream tin). It is the chief source of metallic ti…

re; a common ore of opper, containing copper, iron, and sulphur. It occurs massive and in tetragonal crystals of a bright brass yellow color.

Same as Tetragonal. Dana.

A grayish white zeolitic mineral, in tetragonal crystals. It is a hydrous silicate of alumina and baryta.

A twenty-four-sided solid; a tetragonal trisoctahedron or trapezohedron.

oped alike in the directions of the several lateral axes; -- said of crystals of both the tetragonal and hexagonal systems.

The trapezohedron or tetragonal trisoctahedron; -- so called as being the form of the mineral leucite.

A rare mineral occurring in tetragonal crystals of a white, yellow, or grayish color and adamantine luster. It is a chlorocarbonate of lead.

Manganese dioxide, occurring in tetragonal crystals nearly as hard as quartz.

Same as Tetragonal. Pyramidal numbers (Math.), certain series of figurate numbers expressing the number of balls or points that may be arranged in the form of pyramids. Thus 1, 4, 10, 20, 35, etc., are trangular pyramidal numbers; and 1, 5, 14, 30, 55, etc., are square pyramidal numbers.

Having four angles, and consequently four sides; tetragonal. -- Quad*ran"gu*lar*ly, adv.

Tetragonal.

usually of a reddish brown color, and brilliant metallic adamantine luster, occurring in tetragonal crystals. In composition it is titanium dioxide, like octahedrite and brooklite.

A grayish white mineral occuring in tetragonal crystals and in cleavable masses. It is esentially a silicate of aluminia and soda.

Calcium tungstate, a mineral of a white or pale yellowish color and of the tetragonal system of crystallization.

spinach. See Garden orache, under Orache. -- New Zealand spinach (Bot.), a coarse herb (Tetragonia expansa), a poor substitute for spinach.

A solid bounded by twenty-four equal and similar trapeziums; a tetragonal trisoctahedron. See the Note under Trisoctahedron.

em bounded by twenty-four equal faces, three corresponding to each face of an octahedron. Tetragonal trisoctahedron, a trisoctahedron each face of which is a quadrilateral; called also trapezohedron and icositetrahedron. -- Trigonal trisoctahedron, a trisoctahedron each face of which is an isosceles triangle.…