Mineral Substances of Organic Origin. Guyaquillite. 329 



Suppose our actual knowledge of the almost countless 

 groups of salts already partially studied to be tabulated in a 

 similar manner, and thus compared with the unknown, how 

 few would the cultivated spots appear, how large the water 

 yet to be reclaimed ! And whenever we consider how very 

 few of the properties of the salts longest known have yet 

 been determined with any degree of accuracy, how mere a 

 skeleton does all our chemical knowledge appear ! We hasten 

 after new conquests without waiting to consolidate our do- 

 minion. 



The existence and mode of formation of this salt throws 

 some light on a point of geological interest. As anhydrite 

 occurs only in connexion with rock-salt, it was suggested 

 by Berzelius that the latter might be an igneous and not an 

 aqueous deposit*. Deposited in water the sulphate of lime 

 ought, he reasoned, to be in the state of gypsum, and not of 

 anhydrite ; but the formation of the hemihydrated salt above 

 described, shows that the quantity of water present in such 

 salts does not depend on the presence or absence of water 

 only, but on the united temperature also inider which the 

 crystals are formed. Had the pressure in the boiler been so 

 great as to raise the temperature to 260° Fahr. anhydrite 

 would be formed in nature as it was formed on pouring sul- 

 phuric acid into a solution of chloride of calcium boiling at 

 265° Fahr. 



Two fragments from the exterior of an apparently pure 

 mass of anhydrite from Germany lost when heated to redness 

 about 6 per cent, of water. The interior of the mass lost a 

 mere trace. Does this show any tendency in anhydrite to 

 form the new compound ? 

 Durham, June, 1838. 



XLIV. On the Composition of certain Mineral Substances 

 of Organic Origin. By James F.W.Johnston, A.M., 

 F.R.SS. Lond. and Ed., F.G.S., Professor of Chemistry and 

 Mineralogy, Durham.f 



VI. Guyaquillite. 



T AM indebted to Mr. Brooke for a small quantity of a re- 

 -*• sinous substance said to form an extensive mineral deposit 

 in the neighbourhood of Guyaquil in South America, and for 

 which I propose the name of GuyaquiUite. 



Of this substance I have seen two varieties, one nearly ho- 

 mogeneous of a pale yellow colour, with no resinous lustre or 



• See note If in the preceding page. f Communicated by the Author. 



