468 REPORT OF NATIONAL MUSEUM, 1899. 



According to Griswold stone suitable for the manufacture of whet- 

 stones occurs in quantity in two distinct horizons in the Arkansas novac- 

 ulite series of rocks, both of which are now being worked. The 

 principal quarries are in the massive white beds of the Hot Springs 

 region, the material being mainly of the fine, compact white "Arkan- 

 sas" type. Within a limited region, northeast of Hot Springs, the 

 stone becomes more porous, owing in part to the existence of a larger 

 number of the rhomboidal cavities, and passes over to the Ouachita 

 type. 



The microscopic structure of the Arkansas novaculite is shown in 

 Plate 30, fig.l, the large white areas being angular granules of quartz. 



Owen regarded the Arkansas novaculites as belonging to the age of 

 the millstone grit formation; that is, to the lower part of the Carbo- 

 niferous, and considered them as a sandstone metamorphosed and freed 

 from impurities by the action of hot alkaline waters. State Geologist 

 Branner, however, regards the finer grade of novaculite as a meta- 

 morphosed chert, a conclusion more in accordance with the microscopic 

 structure of the rock, which is more that of chalcedony than of an 

 altered sandstone. Griswold, on the. other hand, regards the novacu- 

 lite as a product of sedimentation of a fine siliceous silt, and of Lower 

 Silurian age, 1 while Rutley 2 considers it as a product of chemical 

 replacement by silica of the calcareous material of dolomite or dolo- 

 mitic limestone beds. 



The view of Suttons quarry No. 7 in Plate 29 shows the novaculite 

 beds dipping 60 to the southeast, the bed of good stone being some 12 

 or 15 feet in thickness. The rock is everywhere badly jointed, in one 

 case mentioned by Griswold as many as six different systems being 

 developed in a single quarry. The natural result is that pieces of only 

 very moderate dimensions are obtainable even under the most favorable 

 of circumstances. Fine veins of quartz intersecting the rock in various 

 directions increase the difficulty of getting homogeneous material and 

 thereby increase the cost of the output. 



The Arkansas stone is now used for many purposes. The whet- 

 stones are used by engravers, surgeons, carvers, dentists, jewelers, 

 cutlers, and other manufacturers of fine-edge tools, and by machinists 

 and woodworkers of the more skilled class. Small whetstones for 

 penknives are made in considerable quantity and some stones are sold 

 for razor hones. 



The stone is also used by wood carvers, jewelers, manufacturers of 

 fine machinery and metal work, and by dentists in various forms of 



1 See Whetstones and Novaculites, by L. S. Griswold, Annual Report of the Geo- 

 logical Survey of Arkansas, III, 1892. This report contains a very full discussion of 

 the Arkansas novaculite in all its bearings. 



2 Quarterly Journal of the Geological Society of London, L, 1894, p. 377. 



