86 PROCEEDINGR OF THE NATIONAL MUSEUM. vol. r,l. 



The bearing on this question of certain relations between constitu- 

 ents may be pointed out here. If the SO3 and P2O5 found in the 

 present specimen be regarded as united with BaO, the amount of 

 the latter necessary would be 3.27 per cent, while 3.12 per cent was 

 found. This essential agreement may be an accident, but the known 

 stability of BaSO^ and Ba3(P04)o suggests the possibility that these 

 compounds are actually present. The ratio of the ALOg to SiOo 

 found is roughly 1 : 2, indicating that these constituents maybe united 

 as a clay of the halloysite group. The FcoOa may well be combined 

 with some of the H2O to form limonite. But there remains about 

 10 per cent of oxides the condition of which is not so clear. Of 

 these, LiaO, Na20,and K.O should be soluble in water, yet waterfalls 

 to extract them from the mineral, so they must be held in some peculiar 

 way. They can not be in the form of manganates (Laspeyres-Dana 

 theory), for their manganates prepared artificially are soluble in 

 water to green solutions. No definite manganites of these elements 

 have ever been obtained artificially. By exclusion, therefore, it 

 would seem that the only form in which these oxides (and, corre- 

 spondingly, the MnO, CoO, and NiO) can be present is as gels, 

 united by adsorption to the MnOo gel, which makes up the bulk of 

 the material. Accordingly, no "mineral composition" is to be de- 

 rived for psilomelanite, but it is to be regarded as composed essen- 

 tially of adsorption products of the various oxides. 



TITANITE OF UNUSUAT. HABIT. 



A yellowish-brown radiated-acicular mineral imbedded in datolite 

 was discovered in 1913 in the northernmost quarry of the group situ- 

 ated on the east side of the Delaware River, 2 miles north of Lambert- 

 ville, New Jersey, by Mr. Oscar Streland, of Philadelphia, and sub- 

 mitted to the writer for identification. Qualitative chemical and 

 optical examination showed it to have the general features of titan- 

 ite, but as this mineral had never before been observed in acicular 

 form further investigation seemed desirable. Mr. Streland and Mr. 

 Henry Munson, of Philadelphia, Idndly presented several small 

 specimens to the Museum (Cat. No. 59206), and of these all but one 

 Avere broken up for examination. As the specific gravity of titanite 

 (3.50±.10) is much higher than that of datolite (2.95±.06) mer- 

 curic potassium iodide solution of specific gravity 3.20 was used to 

 separate them, and about 0.8 gram of the unknown mineral obtained, 

 which proved to be quite homogeneous under the microscope, con- 

 taining only minute amounts of datolite adhering to a few of the 

 yellow grains, and of ilmenite, a mineral sparingly associated. 



The mineral has the following properties : 



