116 Fourth Supplement to Dana's Mineralogy, 



DEMTDOFFITE, JV. Nordenskwld, Bull. Soc. Imp. Nat. Moscou, 1856, ISo. 1, p- 

 128. — This mineral, from Tagilsk in the Ural, is an amorphous species, related to 

 chrysocolla and has gone by the name of blue malachite. It occurs in mammillated 

 crusts, and sometimes the layers alternate -with malachite and tagilite or other phos- 

 pliates. Color sky-blue, sometimes a little greenish. Streak -white. H.::==2 nearly. 

 6.=2-25. Fracture a little waxy. Transparent only on the edges, but more so on 

 being put in water. Porous and adhering to the tongue. B.B. becomes black, and 

 in the inner flame melts easily, giving a black scoria with a metallic lustre exter- 

 nally. Id a glass tube yields water with no acid reaction. With borax fuses in the 

 outer flame easily without intumescence, affording a glass at lirst black and then 

 bluish green on cooling ; in the inner flame the pearl is nearly colorless. Each time 

 on commencing to re-heat the bead, the flame appears greenish. With salt of phos- 

 phorus a skeleton of silica. Composition : 



i Si Cu % fl - P 



31-55 0-53 33-14 3-15 23-03 [10-22] =100 

 Oxygen 16-39 0*25 6-67 060 20-47 5-73 



The rocks at Tagilsk are decomposed along the veins to a great depth. Even to 

 a depth of 500 feet, to which the copper mines descend, the rocks are all disin- 

 tegrated excepting the hmestone about the ore. A large isolated block of malachite 

 was laid bare in 1848 at a depth of 315 feet Sometimes the masses of malachite 

 have within a mass of native copper, surrounded with red copper and malachite 

 and sometimes with Demidofiite, Tagilite, and phosphochalcite. The sulphurets 

 increase in proportion as they descend in the mine. 



Dechenite [p. SGI]. — Fischer and Nessler have described (Leonb. u. Bronn's Jahrb., 

 1855, 570), a supposed new vanadate of lead under the name of Eusy^ichite, which 

 contains, according to their analysis, — 



V 22-69 V 20-49 tb 55*70 Si 0*94 loss 0*18 = 100 



affording the formula t*b V-|-l*bv. It is from Freiburg in Brisgau, where it Is found 

 in nodular and stalactitic forms. H.=3-5. G.=4'945. Color yellowish red, leather- 

 yellow ; streak paler. B.B, fuses to a lead-gray globule and yields lead. Easily 

 soluble in nitric acid. Kenngott observes (Min. Forsch. for 1855) that supposing the 

 acid to be all vanadic, the formula is that of Dechenite, which it much resembles. 



The following note on ArcBoxene^ Dechenite and Eusy^ichite has been communica- 

 ted for this Supplement by Prof. George J. Brush. 



Note by G. /. Brush, — Dr. Krantz of Bonn informed me in the eummer of 1856 

 that V. KobelFs Aroioxene is identical with Dechenite — that it is in fact the same 

 mineral from the same locality. 



Von Kobell in his description of Ariroxene mentions it as occurring at Dahn in the 

 Palatinate, while Krantz gave the locality of Dechenite as Lauter Valley near Nie- 

 der-Schlettenbach. The small village of Dahn is in Lauter Valley near Ifieder- 

 Schlettenbach, so that there is really no difference as to locality. Tlie physical 

 properties of ara^oxene and dechenite, as described by von Kobell and Bergemann, 

 are identical. The analysis of dechenite by Bergemann gives its composition as a 

 simple vanadate of lead tb Vj but v. Kobell's analysis of arfeoxene gives, besides 

 lead and vanadic acid, 16'32 pr. ct. of oxyd of ziac. An authentic specimen of de- 

 chenite obtained from Dr. Krantz, which I have examined, contained a considerable 

 amount of zinc, so that there can be little doubt as to the propriety of uniting the 

 two minerals. 



The new species Eusynchite bears so strong a resemblance to dechenite that I 

 led to make a qualitative examination to see whether it might not also contain 

 zinc. My analysis proved the presence of zinc, but the small amount of mineral at 

 command was not sufficient for a quantitative determination. It is much to be de- 

 sired that some analyst having more of the muieral should make a special examin^^' 

 tion in regard to this point. 



Diamond [p. 24 and I]. — For some years, says Descloizeaux (Ann. des Mines, [6], 

 viii, 304), a variety^ of black diamond has como from a region of arenaceous rocks 

 Bear Bahia in Brazil, which has been known among lapidaries as carbonate. It is 

 essentially crystalline, sometimes in small octahedrons, sometimes massive, compact 

 or cellular. Specimens as large as a nut have rounded edges, resinous lustre, and a 



