MINERALOGY. 473 



riarstig iniue, Pnjsberg, Sweden. It occurs in massive forms, liaviiig- a 

 cohminar or fibrous structure, and shows two unequal cleavages inclined 

 at an anijle of 82i degrees. On the basis of an optical examination it 

 is referred to the triclinic system. The color is rose-red and the luster 

 silky. The hardness is 4 to 5, and the si)ecilic gravity 3.03. An an- 

 alysis yielded: 



Si02 MnO FeO CaO MgO PbO n^O 



43.67 37.04 1.11 8.38 0.15 0.77 7.17 = 90.29. 



This gives as the formula 2 (MnCa).SiO:!+H20, which brings it in com- 

 position near the hydrorliodonite of Igelstriim which is MnSiOj-+-H20. 

 In form and appearance it bears some resemblance to wollastonite and 

 pectolite. It is the most recently formed of the minerals of the Harstig 

 mine, filling cavities between calcite crystals. (Described by G. Flink, 

 in CEfversigt Vet. Akad. Forhandl., Stockholm, 1888, p. 571.) See 

 Inesite, above. 



RtehecMte — A mineral belonging to the amphibole grouj), from the 

 island of Socotra, where it was collected by Dr. E. Riebeck, after wliom 

 it is named. It appears in slender prismatic crystals, having the char- 

 acteristic cleavage imbedded in granite. The color is black. An analy- 

 sis, after deducting 7.12 per cent, zircon, yielded : 



SiOo TcjOj FcO MnO CaO M,i;0 Na-^O K^O 

 nO.Ol 28.30 9.87 0.03 1.32 0.34 8.79 072 = 99.98. 



Itisthns like the pyroxene segiritf^, e.ssentially a silicate of iron sesqui- 

 oxide and soda, and is regarded as occupying the same place among the 

 amphiboles. Tlic mineral arfvedsonite has occupied this position, but 

 recent analyses have made it contain chiefly iron protoxide, and if these 

 are- sustained, riebeckite cannot be united with it. (Described by A. 

 Saner in Zeitschr. dentsch. Geol. Ges., 1888, vol. XL, 138.) 



Rosenbuschite. — See Barkevikite. 



Snlphohalite. — A mineral consisting of the sulphate and chloride of 

 sodium. It was discovered by W. E. Hidden on the hanksite of Borax 

 Lake, San Bernardino County, California, and thus far is extremely 

 rare. It appears in rhombic dodccahedrous, which are transparent and 

 of a faint greenish-yellow collor. The hardness is 3.5, and the specific 

 gravity 2.489. An analysis by J. B. Mackintosh yielded: 



so,, Cl Na^COs 



42.48 13.12 1.77 



or calculating the chlorine and sulphur as combined with sodium only: 



NajSOa NaCl NavCOj 

 75.41 21.62 1.77=98.80. 



This corresponds to 3Na2S04 2NaCl. The name sulphohalite is given in 

 allusion to the unusual composition of the mineral. (Described by W. 

 E. Hidden and J. B. Mackintosh in Amer. Journ. Sci., 1888, vol xxxvi, 

 p. 463.) 



