80 The N.Z. Journal of Science and Technology. [April 
Silica (Si0 2 ) 
Papery 
Material. 
56-08 
Thicker 
Material. 
55-88 
Pilolite. 
54-37 
Alumina (A1 2 0 3 .) .. 
14-02 
19-35 
11-27 
Ferric oxide (Fe 2 0 3 ) 
1-16 
0-88 
0-21 
Ferrous oxide (FeO) 
• 0 
• • 
1-09 
Manganese oxide (MnO) 
. . 
• . 
0-33 
Titanium dioxide (TiO s ) 
Nil 
Nil 
. . 
Lime (CaO) 
0-88 
0-75 
0-98 
Magnesia (MgO) 
8-42 
2-78 
9-49 
Soda (Na 2 0) ... . . 
0-08 
0-20 
• • 
Potash (K 2 0) .. . . 
0-47 
0-32 
• e 
Water at 100° C. . . ... 
6-40 
6-40 
9-26 
Combined water .. - . . 
13-10 
13-20 
13-15 
100-61 
99-76 
100-15 
The fact that the samples differ so widely in the porportions of alumina 
and magnesia without varying greatly in the other constituents suggests 
that the material consists of a mixture of hydrated silicates of alumina and 
magnesia of corresponding composition. Closely related families of silicates 
are well known, such as the kaolinite and serpentine families, in which A1 2 0 3 
in the former is replaced by 3MgO in the latter. Compare the following mineral 
species : Kaolinite (Al 2 0 3 .2Si0 2 .2H 2 0) and serpentine (3Mg0.2Si0 2 .2H 2 0) ; 
pyrophyllite (A1 2 0 3 .4Si0 2 .H 2 0) and talc (3MgO .4Si0 2 .2H 2 0) ; cimolite 
(2A1 2 0 3 .9Si0 2 .6H 2 0) and sepiolite (6MgO. 9Si0 2 .6H 2 0). These minerals 
are crystalline^ and in some one or other of their occurrences have a scaly, 
lamellar, fibrous, or felted structure. Again, when associated with more 
molecules of water, which is expelled at boiling-point, they give rise to a 
series of amorphous mineral species—kaolinite to halloysite, talc to steatite, 
pyrophyllite to montmorillonite, &c. Rectorite, another superhydrated 
kaolinite, is leathery and physically similar to the material here considered. 
Mixtures of the various silicates occur also, as in the minerals saponite . 
arctolite, neolite, and pilolite:' Of “these;™the” last-mentioned, a fibrous, 
tough, and flexible mineral occurring at various localities in Scotland “ in 
granular limestone, in granite veins, and in veins in sandstones and slates,” 
is very similar to the material found near Mahoenui, although containing 
less alumina and more magnesia. Dana, in his System of Mineralogy, 
gives several analyses, of which that nearest to those of the mineral here 
described is tabulated with them. 
The water lost at boiling-point probably does not enter into the com¬ 
position of the molecule, and the analyses have been recalculated with 
the omisssion of such water and also of the soda and potash contained in 
the mineral. The results are here tabulated together with cimolite and 
sepiolite (the German meerschaum). From its manner of formation, im¬ 
purities are sure to be present, and, taking this into account, it seems 
probable that the mineral consists of a variable mixture of molecules of 
cimolite and sepiolite or of related superhydrated minerals. 
Papery 
Material. 
Thicker 
Material. 
Cimolite. 
Sepiolite. 
Silica (Si0 2 ) . . 
. . 59-9 
60-2 
63-4 
60-8 
Alumina (A1 2 0 3 ) 
. . 15-0 
20-8 
23-9 
. . 
Ferric oxide (Fe 2 0 3 ) 
1-2 
1-0 
• . 
. • 
Lime (CaO) 
0-9 
0-8 
• • 
Magnesia (MgO) 
9-0 
3-0 
.. 
27-1 
Combined water 
. . 14-0 
14-2 
12-7 
12-1 . 
100-0 
100-0 
100-0 
100-0 
