NOTITE. 

 Soda .... 

 Lime .... 

 Protoxide of iron . 

 Protoxide of manganese 

 Sulphuric acid 

 Sulphur 



12-24 

 8-14 

 1-15 

 0-50 



11-56 

 1-41 



99-50 



BB becomes colourless when heated, and 

 fuses to a blistered glass. 



Decomposed by muriatic acid, with evo- 

 lution of sulphuretted hydrogen and forma- 

 tion of gelatinous silica. 



Localities. Lake Laach, near Andernach 

 on the Rhine : also at Rieden and Volkers- 

 field. 



Name. After the discoverer, K. W. Nose. 



Brit. Mus., Case 37. 



NoTiTE. A variety of Palagonite from 

 the Val di Noto, the composition of which 



is represented by the formula K^ gi + 3^ gi 



+ 9H. 



Analysis (mean of many), by Von Wal- 

 tershausen : 



36-96 



Alumina 



. 5.25 



Peroxide of iron , 



. 21-66 



Lime . . . • 



. . 3-26 



Magnesia . 



. 11-64 



Soda . 



. 0-97 



Potash . 



. 0-99 



Water . 



. 18-16 



100-00 



Name. From the locality, the Val di 

 Noto. 



NussiERiTE, Danhauser. Occurs in very 

 obtuse rhombohedrons. Colour yellowish, 

 greenish or greyish, with a faint waxy 

 lustre. H. 4 to 4-5. S.G. 5-041. 



Comp. Phosphate of lead and lime with 

 chloride of lead ; containing chloride of lead 

 7-65, oxide of lead 46-50, lime 12-30, prot- 

 oxide of iron 2-44, phosphoric acid 19-80, 

 arsenic acid 406, quartz 7-20 =-99-95, 



BB fuses and solidifies into a whitish 

 angular enamel : with borax forms a yellow- 

 ish glass. 



Dissolves readily, without effervescence, 

 in nitric acid. 



Locality. Nussiere, Dept. of the Rhone, in 

 Prance. 



Brit. Mus., Case 57b. 



NuTTALiTE, Brooke. A variety of Scapo- 

 lite. Occurs in rectangular prisms. Colour 

 white, in some parts yellowish, in others 

 bluish or green. Lustre vitreous, with a 



OBSIDIAN. 261 



play of light on the faces of the prisms 

 similar to that of Elseolite: on surface of 

 fracture resinous. Streak white. H. 4 to 

 5. S.G. 2-7 to 2-8. 

 Analysis, from Bolton, by v. Rath : 



Silica 44-40 



Alumina .... 25-52 

 Peroxide of iron . . . 3-79 



Lime 20-18 



Magnesia . . . .1-01 



Soda 2-09 



Potash 0-51 



Water 1-24 



98-71 

 Localities. Bolton and Boxborough, Mas- 

 sachusetts, in coarse granular limestone, 

 with Epidote and Titanium Ore; Lewis co.. 

 New York. 



Name. After Mr. Nuttall, by whom the 

 first specimens were brought to this country. 

 Brit. Mus., Case 31. 



0. 



Oblique Mica. See Muscovite. 



Oblique Pkismatic Arseniate of Cop- 

 per, Phillips. See Cllnoclase. 



Obsidian. A volcanic glass, produced by 

 the fusion of fel spathic rocks, or those con- 

 taining or composed of alkaline silicates; 

 hence the composition is very variable, and 

 depends upon that of the rock which has 

 been melted down. In fact, Obsidian, Pitch- 

 stone, and Pearlstone, are only different 

 forms of the same mineral, produced by dif- 

 ferent rates of cooling from the melted state ; 

 and any lava or rock containing the neces- 

 sary ingredients may become converted into 

 all or either of these substances, according 

 as it has cooled more or less quickly. Those 

 portions of the fused mass which have been 

 cooled the most rapidly will be converted 

 into Obsidian ; while the inner portions 

 which have cooled more slowly will become 

 Pitchstone, which, in its turn, passes gra- 

 dually into the Pearlstone, forming the cen- 

 tral part. This has been proved to be the 

 case by experiments conducted on a large 

 scale at the Eagle Foundry, at Birming- 

 ham, by Mr. Hawkes, 



" A large mass of Rowley Rag, weighing 

 about 31 cwt., having been melted in a large 

 double reverberatory furnace, at the Eagle 

 Foundry, Birmingham, was broken up, after 

 cooling slowly for thirteen days. It was 

 s3 



