( .^8 ) 



" coast " or quartz cat's-eye is of a quite different character, consist- 

 ing of quartz with included silky fibres of asbestos.) The green 

 alexandrite appears red by transmitted light and generally also by 

 candle light, but green by reflected light or daylight. 



Galcite, OaCOg. — 'In the crystalline limestones. 



Dolomite (CaMg)CO.}. — In the crystalline limestone ; sometimes 

 forming with calcite parallel or ramifying intergrowths. 



Forsterite, MgoSi04. — This colourless mineral is characteristic 

 of the crystalline limestones, where it is extremely abundant. 

 The individuals are usually small. An unusually large crystal 

 in limestone is exhibited ; also some very flattened crystals of a 

 superficially dark colour. Incipient superficial decomposition 

 often gives a dark colour to the crystals. 



Glinohumite,Mg^QAgF)^{^\0^)^. — Thisbeautiful yellow mineral 

 is of rare occurrence in the crystalline limestones. 



Pyroxenes : 



(1) Hypersthene (FeMg)Si03. — One of the most characteristic 

 minerals of the Charnockite Series. 



(2) D topside (CaMg)Si03. — A colourless to pale green pyroxene 

 characteristic of the crystalline limestones. 



(3) Manganhedenbergiie, Ca(FeMn(Si03)2. — Characteristic of 

 the Galle group, and probably common in similar rocks elsewhere. 



(4) Augite, CaMgFe(Si03)o + MgFe(AlFe)o(Si03).3. — Charac- 

 teristic of many pyroxene grauulites. 



(5) Wollasto?iite, CaSiOg. — Characteristic of the rocks of Galle, 

 in which it occurs disseminated, and also in very large individuals 

 in coarse pegmatite veins. It has not yet been found elsewhere 

 in Ceylon. 



Amphiboles : 



(1) Tremolite, CaMg3(Si03)4. — Includes colourless and pale 

 amphiboles associated with the crystalline limestones. 



(2) Hor/ieft^mde, Ca(MgFe) 3(8103)4 &c.— Includes dark amphi- 

 boles occurring in the crystalline limestones and the dark green 

 amphiboles characteristic of many of the more basic varieties or 

 granulites and of contact zones. 



Ilmenite, FeTiOa. — Of widespread occurrence ; the commonest 

 ingredient of ndmbu and black sand. One exceptional and very 

 large specimen is shown. 



Geikielite, MgTi03. — Not known except in Ceylon, where it was 

 found in gem refuse. 



Titanite {Sphene), CaTiSiO.-.— Characteristic of the rocks of the 

 Galle group; common in junction rocks, &c. 



Talc {Steatite), HoMg3(Si03)4.— To be distinguished from mica. 

 Kare as an accessory mineral in crystalline limestones. 



