[ 52 j 



VIII. On Ludlamitc, a new Cornish Mineral. 

 By Frederick Field, F.R.S.* 



LUDLAMITE is found associated with quartz, chalybite. 

 Vivianite, iron pyrites, and mispickel. In the gangue 

 of some specimens galena, blende, and fluor have also been 

 noticed. 



Hardness 3-4. Specific gravity 3*12. Colour clear green, 

 from pale to dark, transparent and brilliant. Streak very pale 

 green, approaching white ; powder greyish white. Before 

 the blowpipe on charcoal, tinges the flame slightly green, 

 and yields a semifusecl blackish residue. 



In closed tubes yields water on heating, decrepitating vio- 

 lently, breaking up into brilliant crystalline plates of an intense 

 bluish-green colour by transmitted light. Soluble in dilute 

 hydrochloric and sulphuric acids ; oxidized and dissolved by 

 nitric acid. Perfectly insoluble in glacial acetic acid. De- 

 composed immediately by boiling with solution of potassium 

 or sodium hydrate into ferrous oxide and phosphate of the 

 alkali metal. Consists entirely, when pure, of ferrous oxide, 

 phosphoric acid, and water. Oxidizes slightly, like Vivianite, 

 by long exposure to air, with the formation of ferroso-ferric 

 phosphate. The crystals contain generally minute particles of 

 chalybite, which are very difficult to separate, also specks of 

 iron pyrites. 



Estimation of Water. — As the mineral, when heated in air, 

 is more or less oxidized, and that very readily, it was evidently 

 necessary to prevent oxidation. The crushed crystals were 

 pressed between folds of warm bibulous paper to remove any 

 small amount of mechanical water, wrapped in thin platinum- 

 foil, and heated to low redness in an atmosphere of carbonic 

 acid. 



0-214 grm. lost 0'036 = 16*82 per cent, 

 0-192 „ 0-033 = 17-18 „ 

 0.230 „ 0-039 = 16-95 „ 



Mean of analyses ... 16-98 per cent. H 2 O. 



Estimation of Iron. — The iron was estimated by a standard 

 solution of potassium permanganate. When the crystals are 

 pure, there is no difference in the quantity of the test-solution 

 employed, whether before or after the addition of a deoxidizing 

 reagent to the solution of the mineral in dilute hydrochloric 

 acid, showing the absence of the higher iron oxides. 



* Communicated by the Crystallological Society, having been read 

 December lo, 1876. 



