66 T. STERRY HUNT : SUPPLEMENT TO 
P = 16:89 and D = 2:64 has V = 6:39. 
sation in similar silicates. 
§ 6. In the species of the colloid type—represented among the various sub-orders of 
We have thus presented three stages of conden- 
TABLE I.— PEcroriroips. 






SPECIES. FORMULA. P D | Vi | x 
| 
Calamine (zn:Si)0, + aq 24°00) 3250) 6:87 10: 
Thorite (th,si,)o0, + 2aq 32.62 | 5.30 | 6.15 | I. 
Cerite . (cesi)o; +1aq 29.80 | 4.90| 6.08! ? 
Gyrolite . (casi;)0; + 1aq ip 
Friedelite (mn,si;)0; + 2aq R. 
Pyrosmalite (fe.si;)0; + lag H. 
Chrysotile (mg;si,)0; + 2aq ? 
Xonaltite (ca,siz)o; + Jaq P 
Plombierite (causi:)0; + 2aq ? 
Dioptase . (ctysie)o; + 1aq 
Pectolite . (CasSi)On + 12q 
Datolite . (ca:sib;)0) +1aq 
Apophyllite . (casi,)0; + 2aq 
Okenite . (casi,)0; + 2aq 




silicates, by the Ophitoids, Pinitoids and Argilloids, and corresponding to the order Poro- 
dini and the various porodic species of Breithaupt—are included, not only pure colloids 
like chrysocolla and allophane, but admixtures of colloids with crystalloids, as in the case 
Tage II.— Prorospatnuoips.! 






SPECIES. FoRMULA. P | DAV EX 
Danalite. - - - | (m,sig)o,3- (m=gl, fe, zn) - @ | 99,15 |3.43/6.76| I. 
Willemite. - -|(zn;si)o, - - - - - - - -| 927.75 |4.18]6.63] H. 
Batrachite. - - | (m,Si,)o, - (m—cas;mgs;) - - | 19.50 | 3.03) 6.43] ©. 
|Tephroite.- - -|(mm,sijjo, - - - - - - -| 25.25 |4.12,6.13| O. 
Knebelite. - - - | (m,si,)o, - (m—fe,:mn,.;) - 25.87 | 4.12) 6.15) ? 
Gadolinite. - - |(m,si,)o, - (m —gl, yt, fe) - 6 | 25.66 |4.20/6.10) ©. 
Helvite. - - - | (msi,)o,-(m=gl,mn)- - =| 20.16 |3.30,6.11| I. 
Leucophanite. - | (m,si,jo;- (m=gl,ca,na) - c | 18.05 | 2.97/6.07| O. 
Wollastonite.- - |(casi,)o; - - - - - - - - | 19.383] 2.92) 6.62) C. 
Tscheffkinite. - | (m,si,)o,- (m=ce,ca,fe) - d | 27.00) 4.26) 6.34) ? 




of partially devitrified obsidian and pitchstone, and of chalcedony, a colloidal aggregate of 
quartz and opal, the latter a typical colloid. Such admixtures, however, having the 

! The formulas employed in calculating the values of P and V for the following species are 
a. Danalite — (gl..fe,.,çmn,.;2n,.8i6.0)0.081-0 
b. Gadolinite — (21). Y t2-00/80:75C 80-2581 1-00 )0-00- 
c. Leucophanite — (ca,.gl;.5na3.08i16-0)0280e 
d, Tscheffkinite — [Damour] ce(o.gs£€9.29Ap-r5Si1-g0ti or70)O3+99: 
