MEJfACANE, AND ITS ORES. 13'^ 



fumislics US here with an easy means of distinguishing thia 

 fossil from other ores of a red colour. Rutile is generalty 

 of cotemporaneous formation with its associated fossits 5" 

 whereas red silver ore, red orpiment, &c. being formed Jtt 

 veins, are always of later formation than the rock on which 

 they are seated. Some systematic writers have confounded 

 it with rubcllitc, with which it has scarcely two characterffiHr 

 common. "^ ''" 



CHEMICAL CHARACTERS. 



Without addition, or even with phosphoric salts, it is in- J^^J^^^^f *^^^' 

 fusible by the heat of the common blow-pipe ; with borax or rutile. 

 alkali, it affords a hyacinth red transparent glass ; with, the 

 heat excited by pure air, it gives a milk white bead, and 

 suffers a considerable loss of weight. It is insoluble in the 

 mineral acids, before it has been melted with alkali, but 

 yii^lds readily to acid of sugar ; is precipitable by acid of 

 galls with a bright red, and by Prussian alkali with an hand- 

 some dark green colour. The method of analysis I shall ' ' r'^^-r 

 omit, as belonging properly to mineralogical chemistry ; the 

 result has shewn that this fossil consists wholly of the calx of 

 Menac. 



GEOGRAPHIC DISTRIBUTION. 



fjJ:-5l 



This fossil has hitherto been discovered in but few places. Geographic 

 and in moderate quantity, principally near Rosenau, in rutile. 

 Upper Hungary; in Mount St. Gothard, in Switzerland; 

 in Fischthai, in the high mountains of Saltzburg; 'near St, 

 Yrieux, in France ; in the province of Burgos, in Spain ; in 

 the forest of Speysart, near Aschaffenberg, in Francbnia; 

 at Beresooskoi, in Siberia ; and Olapian, in Transylvania, 



GEOGNOSTIC OCCURRENCE. 



The Hungarian rutile is found imbedded in a kind of Geoghostic 

 quartz, passing into rock crystal, and fonning nests in mica occurrence of 

 slate ; it is therefore of cotemporaneous formation with the ^"^' ^' 

 rock in which it lies. That from St. Gothard, in Switzer- 

 land, occurs partly in those drusy cavities, which are not 

 unfrequentin granific mountains of high antiquity, lying in 

 or upon the rock crystal, adularia, and foliated chlorite, with 

 which those cavities are lined, and partly dispersed through, 

 N2 or 



