1893.] Mineralogy and Petrography. 45 
Mineral Syntheses.—Bourgeois and Traube” having failed to 
produce carbonates of the magnesium group of elements by the reaction 
of urea, water and metallic chlorides on each other at 130° in sealed 
tubes, have made another attempt at their synthesis by substituting 
potassium cyanate for the urea. The attempt proved successful, 
needles of aragonite and rhombohedra of dolomite and magnesite 
having been produced under the conditions mentioned, when the 
chloride used was a mixture of the magnesium and calcium salts in 
molecular proportions. 
By the slow action of dilute solutions of copper chloride upon freshly 
precipitated lead hydroxide at ordinary temperatures there is produced 
a blue powder consisting of octahedra and, cubes of percylite, with 
which are associated quadruple twins of a colorless mineral supposed 
by C. Friedel” to be phosgenite. 
Crocoite has been obtained by Ludeking” upon allowing a strong 
solution of caustic potash to stand for some time in contact with lead 
chromate in the presence of a little potassium chromate. By using a 
large excess of very strong caustic potash phenicochroite forms. The 
crystallization of the latter substance is due to the abstraction of the 
solvent by the carbon-dioxide of the air, and of the former by a fur- 
ther reaction between the caustic potash and chromic acid. 
New Minerals.—Penjieldite—This mineral, discovered by Prof. 
Genth® on the slags from Laurion, Greece, is evidently produced by 
the action of sea water upon the materials of the slag. It is usually 
in the form of hexagonal prisms with basal planes, or in prisms tapered 
by pyramids. The color is white and the lustre vitreous to greasy. 
An analysis of the tapering crystals gave: Cl = 18.55, Pb = 78.25, 
O = , indicating the formula Pb ©. 2Pb Cl, 
Brazilite is a new tantalo-niobate from the iron mine Jacupiranga, 
in S. São Paulo, Brazil. Hussak* describes it as occurring in the 
magnetite-pyroxene rock called by Derby jacupirangite. It was ap 
rated by washing the decomposed residue of this rock in a miner’s 
pan, and has heretofore been taken for orthite. Its crystallization is 
monoclinic with a: b : e = .9859 : 1 :.5109. A= 98° 457. The 
forms observed in its crystals are oP, œP, «P2', sP œ, OP, Po, 
*Ib., xv, 1892, p- 13. 
“1Tb., xv, 1892, p. 96. 
"Amer. Jour. Sci., July: 1892; p. 57. 
Amer. Jour. Sci., 18 
“Neues. Jahrb. f. Min., ae 1892, ii, p. 141. 
