1891.] Mineralogy and Petrography. 375 
The mineral bears the same relation to calcium molybdate as scheelite 
does to the corresponding tungstate. An isotropic or weakly doubly 
refracting mineral occurs in the nepheline-syenite of a ‘‘ massif” in 
he Kole Peninsula, Russia. Since its properties have not yet been 
fully determined, its discoverer, Ramsay,*! has not yet assigned to it a 
name, The mineral is red and transparent. It fuses easily, and yields 
water. It is attacked by@etids with difficulty, has a low index of re- 
fraction, „Nna = 1.5223, and possesses no cleavage. Its density is 
2.753, and composition : 
SiO, Al,O,Fe,03 MnO CuO MgO NaO K,O Loss 
55-88 15.19 2.69 O83. : 3. OOO GT: aA 
—Leverrierite® occurs in small pseudohexagonal prisms that are 
twinned orthorhombic forms with a prismatic angle of 128°. They 
have a very perfect cleavage parallel to oP, so that they may easily be 
mistaken for mica, Often the prisms are twisted so that they resemble 
worm tubes to such perfection that they have been mistaken for organic 
markings, and have been described under the name ġacilarites. Ac- 
cording to Termier, all specimens of bacillarites examined by him 
are prisms of the new mineral whose composition is H,,A1,Si,O,,. The 
hardness of the substance is 1.5,-and its density 2.3-2.4. The plane 
of its optical axes is œP% , with a abe acute bisectrix normal to 
oP and an optical angle 2V= 45°-52°. It may be distinguished from 
muscovite by its dark color, and from biotite by its weak pleochroism, 
and its weak double refraction. Leverrierite is found as a metamorphic 
constituent in carbonaceous clay slates, and in interstratified carbonif- 
erous eruptives. 
3l Ref. Neues Jahrb. f. Min., etc., 1891, I., p. 98- 
32 Bull. Soc. Franc. d. Min., XIII., 1890, p- 325- 
