366* Dr. Clarke's further Account of Petalite, [May, 



substances exhibiting the remarkable lustre and somewhat of the 

 fracture of Petalite. In the list of these, as a suspicious mineral, 

 to say nothing more of it, I would mention the remarkable 

 variety of quartz which is called by the French quartz gran ; and 

 some of the substances which have received the appellation of 

 compact feldspar ; a name frequently bestowed in a forlorn con- 

 jectural way, when all knowledge of the real nature of a mineral 

 seems to fail. Among the minerals which have received the last 

 appellation, there is a red siliceous stone, found at Gryphytia in 

 Westmania ; which being neither the hornstone of the Germans, 

 nor the jade of the French, was described by some Swedish 

 mineralogists, as a pure hydrate of silica, of the same nature as 

 opal. The red colour of it, inclining to that pinkish hue, which I 

 mentioned as barely discernible in Petalite, induced me to suspect 

 that it also contains manganese ; 1 therefore undertook its 

 analysis, and found it to correspond exactly with Petalite in this 

 respect; probably lithion may also be detected in the same 

 substance although it have escaped my notice. Previously to 

 the enumeration of its constituents, 1 wish to mention that 1 have 

 ascertained the angles of the mineral which J analyzed under the 

 name of petalite; both by the reflecting and by the common 

 goniometer ; and find them to equal 100° and 80°. Its form, 

 therefore, is that of a four-sided prism, with a rhomboidal base, 

 whose obtuse angle equals 100°. 



The red siliceous substance from Gryphytia, was first brought 

 to this country by that enterprising traveller John Fiott Lee, LL.D. 

 of Si. John's College, Cambridge, the intimate friend, and often 

 the companion in his travels of the intrepid and lamented 

 Burckhardt. Dr. Lee had several specimens of this mineral. 

 They were all uniformly of a red colour ; possessing neither more 

 lustre nor translucency than horn. The fracture is rather 

 splintery than conch oidal, resembling that o( flint ; it has also 

 the hardness of flint. Its specific gravity equals 2"71 when 

 estimated in pump water, at a temperature of 56° of Fahrenheit . 

 As this mineral has not yet received any specific appellation, I 

 shall name it Leelite, in memory of the friend from whom I 

 received it, and because this appellation will lead no person into 

 error as to the nature of the substance to which I allude. The 

 manner of its analysis was precisely similar to that which I before 

 described when engaged in the examination of Petalite. 



(A.) — Twenty grains previously triturated in a porcelain 

 mortar were exposed to a strong red heat, during 15 minutes, in 

 a platinum crucible, and lost T '^ of a grain of water of absorption. 



(B.) — Boiled during 15 minutes in nitric acid, diluted with an 

 equal bulk of distilled water, the insoluble part being washed and 

 dried weighed 19-j^ grains. 



(C.) — The supernatant fluid collected from B, added to the 

 repeated washings of the insoluble residue, being with moderate 

 heat evaporated to dryness, there remained a lemon-coloured 



