THE 

 LONDON AND EDINBURGH 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



JUNE 184.0. 



LX VI. On crijstaUized Native Oxalate of Lime. By H. J. 

 Brooke, Esq., F.R.S.*' 



HAVE had in my possession for some months a specimen 



of calcitef in compound crystals of the metastatic form of 

 Haliy, from |- to | of an inch long, with irregular and curved 

 surfaces occasioned by the intersections of the numerous indivi- 

 duals of which the crystals are severally composed, and which 

 stand on a rather soft light gray matrix. It is uncertain from 

 whence the specimen was brought, but Mr. Heuland sup- 

 poses it to have come from Hungary. 



On the crystals of calcite are deposited a few small crystals, 

 from jV^ to :jth of an inch long, of oxalate of lime, which had 

 from their high lustre been supposed to be some ore of lead. 

 It was, however, apparent that they differed in form from all 

 the known lead oi'es, and on examination by Mr. Sandall at 

 Mr. R. Phillips's laboratory, they were found to be oxalate 

 of lime with one proportional of water. 



The crj^stals appear to have bee^: formed contemporaneously 

 with those of the calcite, in which some of them are partly 

 imbedded, a circumstance which excludes the supposition of 

 their being of vegetable origin ; and as only one other oxalate, 

 that of iron, is known to exist in the mineral state, and as 

 it occurs in a bed of wood coal, and the oxalic acid contained 

 in it may be presumed to have been derived from vegetable 

 matter, this oxalate of lime will afford the first instance of 

 the occurrence of oxalic acid as a distinct mineral product. 



The primary form of the crystals is an oblique rhombic 

 prism, fig. 1. P on M measuring 103° 14' and M on M/ 

 100^ 36' : a cleavage parallel to P has induced me to adopt 



* Communicated by the Author. 



-f- In a list of minerals published a few years since, I proposed this name 

 for the common rhombohedral carbonate of lime j calcite and aragonite 

 thus denoting the two varieties of this substance. 



FMl. Mag, S. 3. Vol, 16. No. 105, June 1840. 2 H 



