402 DESCRIPTIVE MINERALOGY. 



Before the blowpipe on charcoal, it inlumesces and melts into a globule of a dark brown or 

 black colour, and which, when the heat is continued, becomes magnetic. Soluble without 

 effervescence in muriatic acid. 



, Varieties. Earthy Blue Iron. This variety of phosphate of iron, sometimes called Native 

 Prussian Blue, occurs in a friable or loosely cohering state. On its first exposure, its colour 

 is grey, yellow or greenish white ; afterwards it acquires a blue colour of different degrees of 

 intensity. 



The Mullicite of Thomson, is also identical with this species. 



Composition. Vivianite — Protoxide of iron 41 .23, phosphoric acid 31 .18, water 27.49 

 (Stromet/e?-). 



Earthy Phosphate — Protoxide of iron 32.00, phosphoric acid 47.50, water 20.00 {Kla- 

 proth). 



Mullicite, from New-Jersey — Protoxide of iron 42.65, phosphoric acid 24.00, water 

 25 . 00, quartz sand 7 . 90 ( Tho7nson). 



All these varieties, therefore, are hydrous phosphates of iron. 



Geological Situation. The crystalline varieties are often found in primary rocks, and in 

 clays associated with bog iron ore. The earthy and friable varieties occur in peat bogs. 

 These are sometimes used as paints. 



localities. 



Vivianite occurs in crystals, in the fissures of the gneiss rock, along with stilbite, feldspar, 

 etc. at Harlem, N. Y. The colour of the crystals is a dirty blue. The form is the primary, 

 with the terminal edges replaced by planes. Before the blowpipe, these crystals melt into a 

 black scoria, which is attracted by the magnet. In New-Jersey, this mineral occurs at Allen- 

 town in Monmouth county, and in various other parts of the State. It generally accompanies 

 bog iron ore and other argillaceous deposits, and is both crystalline and earthy. 



CACOXENITE. 



[From the Greek xaxos, bad, and ?£vos, a guest ; because its presence is injurious to iron ore.] 

 Kakoxcne. Phillips ^ni Muhs, App. — Cacoxenite. Tlwmson. — Variety of Klaprothine. Bcuilant. 



Description.* Colour dull yellow of different tints. Streak yellowish red. It occurs in 

 exti'emely minute filamentous crystals, generally disposed in diverging groups, radiating from 

 a point ; and which are said to be irregular six-sided prisms terminated by pyramids of six 

 faces ; also in the form of a yellowish powder, when it much resembles the common ochrey 



* This mineral was first described by J, Steinmann, Professor of Chemistry in tlie University of Prague. Brewster's Edin- 

 burgh Journal of Scierice. V. 163. 



