_ Atomic Volume of some Minerals. 223 
above in length. The numbers given are 0-5703:1: 0:9089, 
which on doubling the first term becomes 1:1406: 1 : 0-9089. 
IL QUARTZ, Si—CHABAZITE, (Ca, Na, K)3Si2+841 Si2+1st. 
R:R in Quartz =94° 15’; in Chabazite =94° 46’. 
Il. CORUNDUM, AI—PHENACITE, Bes §i, together with Arsenic and others 
of the group on page 220. 
Taking the angle of the rhombohedron of phenacite at 115° 
25’, the axis a=0°6958. The axis a of Corundum = 1°3617, 
which is nearly double that of phenacite (2 x 06958 = 1:3916), 
The angle of the rhombohedron 2R of phenacite is 83° 12’; 
while R: R in corundum is 86° 4’; in Iridium 84° 52’; in Ar- 
senic 85° 04’, 
IV. SCHEELITE, Ga W—(with TUNGSTATE OF LEAD, Pb W and MOLYB- 
DATE OF LEAD, Pb Mo)=FERGUSONITE, Y6 a. 
Tungstate of lime and Fergusonite crystallize in square octa~ 
hedrons which are hemihedrally modified in the same manner. 
In the former the angle of the octahedron is 100° 8’; in the latter 
a corresponding octahedron has the pyramidal angle 100° 28’. 
he axis of Tungsten is given at 1-05, and that of Fergusonite, 
(another pyramid being assumed as fundamental,) at 150; the 
latter is 14 times the former—a simple relation. Tungstate of 
lead, a recognized pseudomorph of Tungsten, has A: A= 99° 43’, 
and Molybdate of lead, also so recognized, has A: A= 99° 40’. 
e also observe that the vertical axis of Zdocrase is about half 
that of Tungstate of lime. 
V. ZIRCON, Zr Si—RUTILE, Ti—TIN ORE, Sn. 
Rutile and Tin ore are recognized isomorphs; the basal angle 
of the octahedral fundamental forms are 84° 40/ for the former 
and 87° 5/ for the latter. In Zircon, the same angle is 84° 20’. 
The axes of rutile, tin ore and zircon are respectively 0-655, 
06743, 0-6405. 
VIL. CINNABAR, Hg S—EUDIALYTE, 283 Si2+2r Si. 
Cinnabar and Eudialyte are rhombohedral. In the former 
R:R=71° 47’; in the latter, =73° 40’. 
VII. BORAX, Na 62+10H—PYROXENE, Rk? Sig—GLAUBER 
SALT, (Na 8+10H). 
In Pyroxene M: M=8796’; OP: P «=106°6! axes 02867 : 1: 0°9506 
In Borax « gio “« — 106°35" 0-2978 : 1: 09489 
Glauber salt is also near pyroxene. It has M: M=86° 31’ and 
7a Pr ow =104° 41’, 
< rring forms. 
Sumed for Epsom salt, would be the form $P of Chrysolite. And if the plan 
in Epsom salt were taken for the fundamental 
(nearly) as for Chrysolite. 
