COMPOUNDS OF CALCIUM. 21? 



carbonaceous material of organic origin, and is proved by 

 the limestones becoming white when burnt. 



Stinkstone, Anthr aconite. A limestone which gives out 

 a fetid odor when struck. This odor is caused by certain 

 bituminous materials present in the rock. 



Lithographic stone. A very compact fine-grained lime- 

 stone of a gray or grayish-yellow color. 



Hydraulic limestone. An impure limestone. It contains 

 silica and alumina in such a condition that, when burned, it 

 will make a cement that hardens under water. 



Diff. Distinguished by being scratched easily with a knife, 

 in connection with strongly effervescing in dilute acid, 

 and its complete infusibility. Calcite is not so hard as 

 aragonite, and possesses a very distinct cleavage, which 

 aragonite does not. 



Obs. Crystallized calc spar occurs in magnificent forms 

 in the vicinity of Rossie, ISTew York. One crystal from 

 there, now in the Peabody Museum at Iscw Haven, weighs 

 165 pounds. Some rose and purple varieties from this 

 region are very beautiful. Large geodes of the dog-tooth 

 spar variety occur in limestone at Lockport, along with 

 gypsum and pearl spar. Leyden and Lowville, JST. Y., are 

 other localities. Bergen Hill, X. J., affords beautiful 

 wine-yellow crystals in amygdaloidal cavities ; also the 

 Lake Superior copper mines. Argentine occurs near 

 Williamsburg and Southampton, Mass. Rock milk covers 

 the sides of a cave at Watertown, X. Y., and is now 

 forming Stalactites of great beauty occur in Weir's and 

 other caves in Virginia and in the Western States ; also in 

 Ball's Cave at Scoharie, N. Y. Chalk occurs in England 

 and Europe, and in Western Kansas in the United States. 

 Granular limestones are common in the Eastern and At- 

 lantic States, and compact limestones in the Middle and 

 Western States, and some beds of the former afford excellent 

 marble for building and some of good quality for stat- 

 uary. 



Any of the varieties of this mineral when burnt form 

 quicklime, heat driving off the carbonic acid and leaving 

 the lime in a caustic state. In this state it is used for mak- 

 ing mortar by mixing with water and sand ; a calcium 

 hydrate results which becomes slowly carbonated through 

 carbonic acid in the atmosphere. See further the chapter 

 on Rocks, for the uses of limestone. 



