DELESSE — SACCHAROID LIMESTONE OF THE VOSGES. 21 



the geodes that the fine transparent crystals* of carbonate of lime 

 are seen to terminate. 



According to Monnet this limestone is magnesian, but the experi- 

 ments M. Delesse has made together with M. Carriere show that, 

 when it is freed from the magnesian silicates disseminated within it, 

 it contains traces only of magnesia. This limestone is worked at 

 some places for cement (hydraulic lime) ; on which subject M. De- 

 lesse offers some observations (p. 151). 



The minerals disseminated in the limestone of the St. Philippe 

 quarry are Mica (Phlogodite), Pyrosklerite, magnetic and ordinary 

 Iron-pyrites, Spinelle, Sphene, and Graphite. These are described 

 in full, p. 151-161. The dissemination of the mica converts the 

 limestone locally into a Cipolino. Orthose, Oligoclase, Pyroxene 

 (Melacolite), Amphibole, and Sphene (see p. 161-166) occur in 

 small and very complex veins traversing the gneiss ; and most of 

 them are found also in nodules in the limestone, where they are 

 associated with one or more of the disseminated minerals. The 

 minerals in the veins have their crystals usually better developed than 

 those in the limestone. The St. Philippe limestone is not traversed, 

 like that of Chippal, by veins of granitoid rock with an orthose base ; 

 but it contains a great number of nodules, generally felspathic, which 

 are met with in most of the saccharoid limestones. These M. Delesse 

 proceeds to describe in detail (p. 166-172). They are elongated and 

 flattened ; and they form irregular and discontinued beds, which are 

 generally parallel to the lamination both of the limestone and the 

 gneiss. Sometimes, however, the parallel series of nodules at one level 

 are comiected with those at another by strings of similar nodules run- 

 ning across the lamination. These nodules correspond, in their very 

 irregular form and disposition, with the equally irregular veins in the 

 gneiss. The nodules are composed of several concentric, ellipsoidal 

 zones of three minerals, separated one from another as distinctly as 

 the nodules are from the limestone, and succeeding each other pretty 

 constantly in the following order from without inwards, — Mica 

 (Phlogodite), Pyrosklerite, and Felspar (Halleflinta) . The felspar, 

 however, frequently disappears, leaving the other two minerals to 

 constitute the nodule. The other minerals that occur in these no- 

 dular and drusic bodies are Kaolin, Orthose, Sphene, Amphibole, 

 Pyroxene, and Quartz. In some peculiar nodules saccharoid lime- 

 stone is found, with Magnetic-pyrites and Graphite. 



At St. Philippe the felspar, whatever may be its character, always 

 occupies the centre of the nodules, and M. Delesse has not found it 

 in isolated and distinct crystals like those disseminated in the sac- 

 charoid limestone of Baltimore, Col du Bonhomme (Mont Blanc), 

 Kaiserthal, or in the metamorphosed limestone with Gi-yphcea arcuata 

 of St. Laurent (Saone-et-Loire). 



The gneiss, which is well developed in the neighbourhood of Sainte- 



Marie-aux-Mines, generally contains Orthose, Quartz, and Mica, and, 



in certain cases, hornblendic Amphibole, Garnet, Graphite, &c. 



(p. 172, &c.) The gneiss that is in contact with the St. Philippe 



* See Memoir, I. c. p. 150. 



