TAB, XXVIII. 



FERRUM sulphuratum. 

 Silky filamentous Sulphate of Iron. 



Class 3. Metals. Order 1. Homogeneous. 

 Gen. 7. Iron. Spec. 6, Sulphate of Iron. 



Div. 2. Imitative. Far. White Silky. 



1 ab. 23 shows the beginning of this white silky substance. 

 by means of common moist air decomposing the pyrites, 

 which is held in the black clay in such abundance in this 

 specimen, as to separate and divide it so confusedly, that it 

 is only recognizable by the little thin flakes, which still give 

 out small floccose particles if in a damp place. The green 

 crystallized parts in this specimen are also forming into 

 white woolly fibres. Whitby, in Yorkshire, has of old been 

 famous for alum works, as have other parts of the same 

 county. My kind friend the Rev. James Dalton was so 

 good as to send me specimens of alum ore from Mr. 

 Baker's Boulby works. It is a more compact ore than that 

 from Glasgow. Dr. Travis, of Scarboro', gave, me some 

 from Skowbrow, among which a baked specimen has some 

 of the silky filaments remaining, as in Tab. 23. Alum has 

 not been discovered native in England. It is said to be 

 found abroad in octaedral crystals, which is the form of 

 the artificial ones; Of these I have a most superb speci- 

 men, sent by the Rev. James Dalton, from Mr. Baker's 

 alum works above mentioned; also some beautiful little 

 crystals formed by agitation in a wine-glass, showing the 

 lesser octaedrons within the larger, and some curious mo- 

 difications. 



The crystallized specimen from Scotland has a prism. 



