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COMMON OPAL. The Gemeiner opal 



. of Werner. L'Opale commune of 



Broehant. Quartz resinite commun 



of Haiiy. A subspecies or variety 



of opal. See Opal. 



COMMON GAENET. (The Gemeiner 

 granat of Werner.) An earthy 

 mineral of a reddish-yellowish, or 

 blackish - brown color, differing 

 from precious garnet only in being 

 opake or translucent. It occurs in 

 granular masses, and crystallized 

 in dodecahedrons. See Garnet. 



COMPA'CT. A term used in mineral- 

 ology when no particular or distinct 

 parts are to be discerned in a 

 mineral ; a compact mineral cannot 

 be cleaved or divided into regular 

 or parallel portions. It is some- 

 times confounded with the term 

 massive. Phillips. 



COMPACT FELDSPAR. The name assigned 

 to one of the feldspathic trappean 

 rocks. 



COMPEE'SSED. (compressus, Lat.) 



1. In botany, leaves are so termed 

 when flattened laterally. 



2. In conchology, having one valve 

 flatter than the other. 



CO'MPTONITE. A mineral thus named 

 after Lord Compton, who first 

 brought it to England, it is found in 

 the erupted matter of Yesuvius. 



CONCAMEEA'TION. (concameratio, Lat.) 

 An arched chamber. In conchology, 

 concamerations are those small cham- 

 bers into which inultilocular shells 

 are divided by transverse septa, as 

 in the nautilus, ammonite, &c. 



CONCE'NTEIC. (concentrique, Fr. con- 

 centrico, It.) Having one common 

 centre, as the coats of the onion; 

 running to a centre. A term 

 applied to the direction taken by 

 the lines of growth in spiral bodies. 



CONCE'NTETC LAME'LLAE. A term used 

 to describe the appearance of a 

 body which being of a spherical 

 form has received succeesive cover- 

 ings or depositions. 



CO'NCHIPEE. A class of mollusca, 

 the constructors and inhabitants 



of bivalves. All turbinated and 

 simple shells are constructed by 

 molluscs of a higher order than the 

 conchifers, which construct bivalves; 

 the former have heads and eyes; 

 conchifers are without either, and 

 possess but a low degree of any 

 other sense than touch and taste. 

 Thus the whelk is an animal of a 

 higher order than the muscle or 

 oyster. BucUand. 



CONCHI'FEBA. Constitues the second 

 class of Mollusca. It comprises 

 the cockle, oyster, mussel, and all 

 ordinary bivalve shells. 



CO'NCHITE. } (conchytes, Fr. coquittes 



CO'NCHYTE. j pttrifies.} A petri- 

 fied, or fossil, shell. 



CO'NCHOID. In geometry, the name 

 given to the curve invented by 

 Nicomedes. 



CONCHOI'DAL. Shelly; shell-like. The 

 fracture of flint is said to be con- 

 choidal, that is to resemble a shell, 

 having convex elevations and con- 

 cave depressions. 



The surface of fracture is termed 

 conchoidal when it more or less 

 resembles the appearance of a shell ; 

 thus, there are the perfect, imper- 

 fect, large, small, and flat con- 

 choidal. 



CONCHOIDAL HOENSTONE. The Musch- 

 licher Hornstein of Werner. A 

 subspecies of Hornstone, occurring 

 in metalliferous and agate veins, 

 also in striped jasper, and in 

 pitchstone porphyry. See Horn- 

 stone. 



CONCHOLE'PAS. A genus of oval, 

 vaulted, univalvular mollusks ; one 

 species only is known, the concho- 

 lepas Peruviana, brought from Peru. 



CONCHO'LOGY. (from KO^XV, concha, 

 and XoV/os, Gr. conchyliogogie, Fr.) 

 That branch of natural history 

 which treats of testaceous animals, 

 or animals having a testaceous 

 covering, whether they inhabit the 

 ocean, or fresh water, or the land. 



It is upon the exclusive shape 

 of the shell, and not the animal 



