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Fine particles of stone, esp. of siliceous stone, but not reduced to dust; comminuted stone in the form of loose grains, which are not coherent when wet. That finer matter, called sand, is no other than very small pebbles. Woodsward.

A rock made of sand more or less firmly united. Common or siliceous sandstone consists mainly of quartz sand.

See Siliceous.

tensive order of Porifera, which includes those that have the skeleton composed mainly of siliceous fibers or spicules.

om lime-bearing waters; calcareous tufa; travertine. -- Ceraunian sinter, fulgurite. -- Siliceous sinter, a light cellular or fibrous opal; especially, geyserite (see Geyserite). It has often a pearly luster, and is then called pearl sinter.

Any small calcareous or siliceous body found in the tissues of various invertebrate animals, especially in sponges and in most Alcyonaria.

A division of sponges including those which have independent siliceous spicules.

A genus of siliceous spongea found in fresh water.

One of the microsporic siliceous spicules which occur abundantly in the texture of sponges, and are sometimes found fossil, as in flints.

ites and allied genera. These sponges have a fine and compact texture, and contain minute siliceous spicules.

A division of Spongiæ in which the spicules are siliceous and have four branches diverging at right angles. Called also Tetractinellinæ.

A siliceous stone of a yellow color and chatoyant luster, obtained in South Africa and much used for ornament. It is an altered form of the mineral crocidolite. See Crocidolite.

A delicate, hairlike siliceous spicule, found in certain sponges. Trichite sheaf (Zoöl.), one of the small sheaflike fascicles of slender setæ characteristic of certain sponges. See Illust. under Spicule.

ought from Tripoli, used in polishing stones and metals. It consists almost wholly of the siliceous shells of diatoms.

Any one of numerous species of siliceous fossil sponges belonging to Ventriculites and allied genera, characteristic of the Cretaceous period.

nge (Euplectella speciosa) native of the East Indies. It consists of glassy, transparent, siliceous fibers interwoven and soldered together so as to form a firm network, and has long, slender, divergent anchoring fibers at the base by means of which it stands erect in the soft mud at the bottom of the sea. Called also…

nat.) See the Note under Eye. -- Vitreous sponge (Zoöl.), any one of numerous species of siliceous sponges having, often fibrous, glassy spicules which are normally six-rayed; a hexactinellid sponge. See Venus's basket, under Venus.