1866.] KING AND EOWNEY— ^' EOZOONAL EOCK." 209 



YII. " Sarcode-cliamhersJ' 



As already noticed, the granules considered to represent these parts 

 are simulated by wavellite. The same may be said of prehnite and 

 several other minerals. The imbedded aggregations of garnet and 

 leucite may be regarded as modified examples. "We often find a 

 close resemblance between them and the concretions of native copper 

 in porphyry from Canada, of olivine in lava from the Ponza Islands, 

 and of small zeolitic kernels in amygdaloidal trap. The crystalloids 

 of pargasite, whether imbedded in calcite or in woUastonite, are even 

 closer parallels. The isolated grains of coccolite, diopside, and other 

 minerals, in Tyree marble, are strictly analogous to the large gra- 

 nules of serpentine isolately dispersed through the calcite of some 

 specimens of Ophite from Lisoughter*. Chondrodite frequently 

 affords cases identical in every respect with the ^' chamber- casts:" 

 specimens of this mineral from New Jersey are common in a finely 

 granular state: the grains, which are imbedded in calcite, press 

 closely against one another, their individuality being defined only by 

 faint segmentations ; or, lying more or less apart, they are either 

 completely separated or attached to one another by stolon-like necks 

 of varying lengths. 



The characters and circumstances of condition of chondrodite, when 

 it occurs as just mentioned, are so similar to those displayed by 

 serpentine in some varieties of " eozoonal " Ophite, especially the one 

 examined by us from the State of Delaware (also the variety re- 

 presented in figure 13, PI. XY., from Lisoughter, in which the gra- 

 nules are large, often isolated, and unusually wide apart), that it is 

 impossible to resist believing in the complete genetic identity of the 

 two minerals. Nay, carry the examination as far as it is possible, 

 we feel certain that the result will be a full and unqualified surrender 

 to this belief. If, as Dr. Dawson observes, the granules of serpen- 

 tine in Grenville Ophite have "no appearance of concretionary struc- 

 ture," certainly the same must be said of the grains of chondrodite, 

 pargasite, and coccolite in the precited cases. Moreover, if it be ad- 

 mitted that the former are '• casts of sarcode-chambers," the same 

 admission must be made with respect to the latter. 



Sir William Logan has noticed two remarkable varieties of "eozoonal rock,'' 

 identical with Ophite in structure, but differing from it mineralogically. In 

 one of them, occurring at Burgess, the granules or plates are composed of dark- 

 green loganite, and the intervening spaces, or matrix, of dolomite ; while in the 

 other, from the Grand Calumet, the former consist of "crystalline white 

 pyroxene " or diopside, and the latter of calcite. Sir William remarked in 1859, 

 with reference to these two varieties, that if they "are to be regarded as the 

 result of unaided mineral arrangement, it would seem strange that identical 

 forms should be derived from minerals of such different composition." Hence, 

 also observing their structure to have a resemblance to that of Stromatopora 

 rugosa,he was led to suppose both varieties to represent a fossil. (See Geology 

 of Canada, 1863, pp. 48, 49 ; and Quart. Journ. Greol. Soc. vol. xxi. p. 48.) At 

 first sight, we admit, there is some reason for this conclusion ; but when it^ is 

 considered that serpentine and diopside are mutually^pseudomorphous, and that 



* Specimens of this rock from other places in Connemara, after having been 

 immersed for a few hours in dilute hydrochloric acid, are often resolved into a 

 mass of isolated granules scattered over the bottom of the vessel. 



