23^ Intelligence and Miscellaneous Articles, 



all the crystallized forms, consist of 1 equiv. of titanic acid and 

 1 equiv. of protoxide of iron (protoxide of manganese or magnesia). 



2. Magnesia is an essential constituent of all these ores. In the 

 crystallized mineral from Layton, the magnesia amounts to 14 per cent. 



3. According to Mosander's theory, the titaniferous iron ores are 

 either simply titanates of protoxide of iron, FeO, Ti O'-, with isomor- 

 phous admixtures of titanate of magnesia, or mixtures of such with 

 sesquioxide of iron, for the most part in simple proportions. 



4. The theory of H. Rose, that these ores consist of isomorphous 

 sesquioxides of titanium and iron, would require the assumption of 

 a sesquioxide of magnesium. 



5. The author prefers Mosander's theory for the present state of 

 our knowledge. 



6. Iniserine.wefindgrainsconsistingofFeOjTiO-andSFe^O^TiO'^. 



7. No titaniferous iron crystallizing in regular octahedrons is 

 known. The dense masses or octahedral grains which contain tita- 

 nium appear to be mixtures. 



8. The crystallized magnetic iron ores contain no titanium ; they 

 consist of one atom of protoxide and one atom of sesquioxide. 



9. All the Elba iron ore does not contain titanium ; but all, like 

 that from Vesuvius, contains magnesia and protoxide of iron. 



10. The strongly magnetic octahedrons from Vesuvius, hitherto 

 considered as a specular iron, which are accompanied by rhombohe- 

 drons of specular iron, contain in part large quantities of magnesia, 

 and in part protoxide of iron. They consist either of magnetic iron 

 which has been partially converted into sesquioxide of iron, as well 

 as of the isomorphous combination MgO FeO^ ; or, as is more pro- 

 bable, the two protoxides are isomorphous with sesquioxide of iron, 

 which is itself dimorphous. — Poggendorif's Annalen,\o\. civ. p. 497. 



ON GUAYACANITE, A NEW MINERAL SPECIES FROM CHILI. 

 BY FREDERICK FIELD*. 



I send you a specimen of a mineral from the Cordilleras of Chili, 

 which appears to me highly interesting. It consists entirely of cop- 

 per, arsenic, and sulphur, having the following composition — 



Copper 48o0 



Sulphur 31-82 



Arsenic 19'14 



Iron, silver traces 



99-46 

 — and consequently has the following formula, 3Cu'^S + AsS*, and 

 may be considered as a tribasic sulpharseniate of copper, like the 

 artificial tribasic sulpharseniate of potassium, in which that metal is 

 replaced by Cu-. Hardness, 3'5 to 4. Spec. grav. 4'39. 



You will see it resembles Tennantite, in which the arsenic takes 

 the place of the iron, — a specimen of Tennantite having the follow- 

 ing value: Cu, 482; As, 12-5; Fe. 9-0; S, 31-14. I have pro- 

 posed the name Guayacanite for this new species, as the mineral 

 was first brought to the large copper-smelting works of Guayacana. 

 * From a Letter to Prof. Dana iu Silliman's American Journal for Jan. 1859. 



