On Ludlamite, a new Cornish Mineral. 



53 



Mineral. 



Tei* cent. Per cent. FeO. 



0-191) gave 40-80 iron = 52'45 



0-184 „ 41-24 „ =53-02 



0-243 „ 41-13 „ =52-85 



0-201 ,. 40-95 „ =52-64 



Mean of iron 41-03 



Mean of ferrons oxide 52*76. 



Estimation of Phosphoric Acid. — The phosphoric acid was 

 estimated as magnesium pyrophosphate. 



Mineral. Mg 2 " P 2 O r Per cent. P 2 5 . 

 0-214 gave 0-101 = 30'13 

 0-236 „ 0-111 = 30-09 



Mean of analyses 30*11. 



This gives a formula closely corresponding to 

 7FeO ; 2P 2 5? 9H 2 0* ? 

 which requires the following numbers: — 



Calculated. Found. 



7FeO 53-05 52*76 



2P 2 G 5 29*88 30*11 



9H 2 17*05 16*98 



99*98 99*85 



That different specimens of the mineral vary somewhat in 



their composition there can be little doubt. Owing to the 



kindness of Mr. Ludlam and Mr. Tailing, I had sufficient for 



many other analyses, not published here ; and in one or two 



* Ludlamite is doubtless a basic ferrous phosphate • and its relation to 

 Vivianite or normal ferrous phosphate may with much probability be re- 



l£e 



presented by the following formulas : 

 (O 



PO ^o 



(O 



10 



PO \o 



(O 



Vivianite. 



Fe 



Fe 

 Fe 



PO 



PO 



PO 



PO 







o 





 O 



o 



°i 



of 





 



O 



Fe 



Fe 



(FeOH)+8H 2 



Fe 



(FeOH) 



Fe 



81* 



Ludlamite. 



It may be regarded, in fact, as formed by the addition of a single mole- 

 cule of ferrous hydrate, Fe(OIl) 2 , to two molecules of Vivianite, this ad- 

 dition being accompanied by the separation of a part of the water of crys- 

 tallization of the latter. 



