312 



REPORT OF NATIONAL MUSEUM, 1899. 



from Dana's Mineralog}' as .showing- variation in the composition suffi- 

 ciently for present purposes: 



Constituents. 



Silica (SiOa) 



Tliorina (TliOo) 



Alumina ( ALOa) 



Iron sesquioxide ( Fe.i0,j) 



Cerium sesquioxide (Ce.,03) 



Didymium sesquioxide (DioOj)- . 

 Lanthanum sesquioxide (La.)0:j) 



Yttrium sesquioxide (Y0O3) 



Erbinum sesquioxide (EroOs) ... 



Iron protoxide (FeO) 



Manganese (MnO) 



Lime(CaO) 



Magnesia (MgO) 



Potasli (KoO) 



Soda (Na^O) 



Water (HoO) 



31.63 

 0.87 



13.21 

 8.39 

 8.67 

 5.60 

 5.46 

 0.87 

 0. 52 

 7.86 

 1.60 



10.48 

 0.08 

 0.28 

 None. 

 3.49 



99.07 



33.03 

 1.12 

 17.63 

 5.26 

 2.84 

 7.68 



None. 

 2.92 



None. 

 7.01 

 0.64 

 12. 78 

 0.11 

 0.40 



None. 

 9.37 



100.79 



30.04 



None. 



16.10 



5.06 



11.61 



5.39 



4.11 



None. 



None. 



9.89 



Trace. 



13. 02 



1.11 



0.02 



0.28 



2.56 



99.19 



(I) Hittero, Norway; (II) Ytterby, Sweden; (III) Nelson County, Virginia. 



When in crystals often in long- .slender nail-like forms (orthite); also 

 massive and in embedded granules. Color pitch black, brownish, and 

 3^ellow. Brittle. Hardness 5.5 to 6. Specific gravity 3.5 to 4.2. 

 Before the blowpipe fuses and swells up to a dark, slaggy, magnetic 

 glass. 



Localities and mode of occurrence. — The more common occurrence is 

 in the form of small acicular cr3'stals as an original constituent in 

 granitic rocks. It also occurs in white limestone, associated with mag- 

 netic iron ore, and in igneous rocks as andesite, diorite, and rlwolite. 

 At the Cook Iron Mines, near Port Henry, New York, it is reported 

 as occurring in great abundance and in crystals of extraordinary size, 

 in a gangue of quartz and orthoclase. 



The variety orthite occurs in forms closely simulating rusty nails in 

 the granitic rock about Brunswick, Maine. In Arendal, Norway, it 

 is found in massive forms (Specimen No. 60853, U.S.N.M.). At Finbo, 

 near Falun, Sweden, in acicular crystals a foot or more in length. In 

 Amherst and Fauquier counties, Virginia, it occurs in large masses 

 (Specimen No. 68661, U.S.N.M.) from Fauquier County, as it also does 

 near Bethany Church, Iredell County, North Carolina, and Llano 

 County, Texas (Specimen No. 62756,' U.S.N.M.). At Balsam Gap, 

 Buncombe Count}", North Carolina, it occurs in slender ciystals 6 to 

 12 inches long and in crystalline masses, in a granitic vein and under 

 similar conditions at the Buchanan and Wiseman mines in Mitchell 

 County. 



Uses. — See under Monazite, p. 383. 



