196 Scientific Intelligence — Miner aloay . 



correct conclusions as to their true composition. Before analysing 

 such substances, a microscopical examination should never be omit- 

 ted. The microscope, however, may also deceive us, for it can by 

 no means be asserted, that all the interposed bodies which are im- 

 bedded in a transparent mineral are invariably darker in colour than 

 the mass of the latter. With respect to opaque minerals, the micro- 

 scope is of course useless. Many variations, of greater or less amount, 

 which occur in exact analyses of one and the same mineral, are un- 

 doubtedly caused by the presence of interposed bodies. This much, 

 however, appears to be proved, that it is chiefly those minerals only, 

 which are remarkable for distinct cleavage planes, that are liable to 

 this intermixture with foreign matters. — (Pot^^eJic/or^s Annals, 

 vol. Ixiv. pp. 153-169.) 



23. Tenorite, a Xew Mineral Species. — This name has been given 

 by Semmola to a newly distinguished substance, in honour of Tenore, 

 the president of the Neapolitan Academy of Sciences. It is pure 

 crystallized oxide of copper, and occurs not unfrequently in the 

 smaller crater-openings of Vesuvius, more particularly in that of the 

 year 1760. It is found in long hexagonal, triangular, or irregular 

 scales, which have a metallic lustre, and a colour varying from steel 

 grey to black ; and which are from one-twentieth to one-third of an 

 inch in diameter. The streak is black. It is soluble with effer- 

 vescence in acids, and conducts itself before the blowpipe like pure 

 oxide of copper. — [JBerzdius'' Jahres-Bericht, 24iA year, p. 282 ; 

 and Opere Minori di Giovanni Semmola, p. 45.) 



24. Thomdite, a New Mineral Species. — Mayer describes under 

 this name, a carbonate of iron found in 1843, at the Bleis-Bach, 

 near the Scheurener Stce<!, in the Siebengebirge, and which, al- 

 though undoubtedly belonging to the genus Sphserosiderite, does 

 not resemble any of the known species. When first obtained from 

 the clay in which it forms a stratum, this iron ore is of bluish 

 colour, moist, and so soft that the largest pieces crumble in the 

 hand. After it has been exposed for two days to the open air, 

 the colour changes to a pale honey yellow, and the mineral be- 

 comes perfectly dry and compact. The Thomaite, so named in honour 

 of Professor Thoma of Wiesbaden, presents the following oryctognos- 

 tical chai'acters : the crystals are rectangular octahedrons, which are 

 composed of individual crystals and grains ; fracture, large granular ; 

 lustre on the fresh surfaces pearly ; specific gravity = 3'10 ; streak 

 white. The analysis afforded 



Protoxide of iron, . . , 53 72 



Silica, 6-04 



Alumina, 4'25 



Lime, 1-52 



Magnesia, 0"43 



Protoxide of manganese, . . 0"65 



Carbonic acid, .... 33-39 



100-00 



