EXITELE. 



yiauber Salt from Vesuvius, containing 

 only two atoms of water instead of ten. 



Comp. Na S + 2H, 



Localities. Important deposits of this salt 

 occur near Lodosa in Navarre, and otiier 

 parts of Spain, especiallj'- at Calatayud, in 

 Catalonia; it also forms veins at the salt 

 mines of Villafranca (Basses Pyrenees), 



Name. From i^a^Biai, to effloresce, and a^«?, 

 salt. 



ExiTELE, Beudnnt. From W^yMi, vaporis- 

 able. See Valentinite. 



Eye-Agate, or Eyestone. The name 

 given to those kinds of circle- A gate in 

 which the central part shows spots more 

 highly coloured than the other portions of 

 the mass. The name Eyestone is also ap- 

 plied to stalactitic carbonate of lime, where 

 slices, cut at right angles to the axis, 

 display a darker coloured spot in the centre, 

 presenting a fanciful resemblance to the 

 pupil of the eye. 



M. P. G. Horse- shoe Case, No. 387, from 

 the Roman states. 



Fahl-ore, Jameson ; Fahlerz, Werner. 

 See Teteahedkite. 



Fahles Rothgiltigerz, Hausmann. A 

 variety of Miargyrite, from Andreasberg, in 

 the Harz, in which part of the antimony is 

 replaced by arsenic. 



Fahlunite. a hydrated variety of lolite, 

 occurring massive and in six-sided prisms. 

 Colour dark reddish -brown, sometimes green 

 or black, and opaque, but yellowish-brown 

 by transmitted light, and translucent in 

 thin fragments. H. 3. S.G. 2-74. 



Comp. 2(K, Ca, Mg, Mn, Fe), 2 Al, 5 Si, 

 3 H. (Gmelin.) According to Dana, Fahlun- 

 ite is equivalent to (lolite + 6 H), but the 

 water is not a constant quantity. 



Analysis, from Terra Nova Mine, by 

 Wachtmeister : 



Silica 44-60 



Alumina .... 3010 

 Protoxide of iron . . . 3-86 



Potash 1-98 



Magnesia .... 675 

 Protoxide of manganese . 2'24 



Lime 1*35 



Soda, hydrofluoric acid . trace 



100-23 

 BB becomes colourless, cracks and swells 



FAROELITE. 135 



up slightly, fusing at the edges to a glass ; 

 with borax or salt of phosphorus melts 

 slowly to a glass, which is slightly coloured 

 bj' iron. 



Locality. Fahlun, in Sweden (whence the 

 name, Fahlunite), with lolite, in Chlorite 

 Slate. 



Brit. Mus., Case 32. 



Fallow Copper Ore, Kirwan. See Te- 



TEAHEDEITE. 



False Topaz. A name given by lapi- 

 daries to a light yellow pellucid variety of 

 Quartz-crystal, ranking next to Amethyst 

 in value. It may be distinguished from 

 yellow Topaz (for which, when cut, it is 

 frequently substituted), by the difference of 

 its crystalline form, the absence of cleavage, 

 inferior hardness, and lower specific gravity. 

 The colour is of different degrees of inten- 

 sity, and is frequently combined with a 

 smoky brown, forming a tint of much 

 warmth and richness when not in excess. 

 In this respect it is equal to the Saxon 

 Topaz, though inferior to the Brazilian. It 

 is generally made into seals and brooches, 

 and appears to the greatest advantage when 

 cut in steps. The breadth of the table should 

 be in porportion to the fulness of the colour, 

 and, if deficient in the latter respect, it should 

 be carefully set with a proper foil. (Mawe.) 



It is found in the Brazils, and is some- 

 times called False Cairngorm of Brazil. 



M. P. G. Horse-shoe Case, No. 509. 



Faroelite, Heddle, Greg §* Lettsom. A 

 mineral intermediate in composition be- 

 tween Soda-Thomsonite and Mesolite. Rhom ■ 

 bic: primary form a right rhombic prisni. 

 Colour white, bluish, yellowish, greyish. 

 Lustre pearly or vitreous. Cleavage perfect. 



Comp. Mesolite with one equivalent less 



of silica; or (Na, 2Ca)2Si + 3(Ai Si)+8H 

 = silica 42-45, alumina 28-27, lime 10 '29, 

 soda 5-75, water 13-24=100-00. 



fi- 



Fig. 186* 



Localities.— Scotch. Isle of Skye (Jig. 

 186*.) at Portree in confused white globules ; 

 Storr in bluish-white implanted spheres with 

 Mesolite; near Talisker in white radiated 

 and implanted globules, with Laumonite 

 and Tesselite ; at Uig, in white radiated 

 globules, lining cavities in trap. 



Irish. Antrim ; at Agnew's Hill at 

 Portrush in greenstone. Black cave near 

 Larne, at the N.W. of liathlin Island. 

 k4 



