Ay Molecular 3 
DESCRIPTION OF ROCKS AND ANALYSES 39 
 drying of the sphaerule: concentric shrinking cracks appear on them. 
_ The glassy groundmass of the rock often seems to change into a 
substance of similar character, partially when presenting greater 
masses, also with sensible birefraction and within a greater scale 
of colours. On the other hand, the glassfchanges apparently in an 
other substance too, having some community with. the serpentine 
substance mentioned above; this alteration process is characterized 
by more greenish tints. — The matter of the sphaerules presents 
some resemblance to the „hullite“, and is described by various 
‚authors under different names; it does accompany basalt and dia- 
base flows of several types.’ Around the sphaerule cavities tangen- 
tially placed feldspars form a complete circle. 
A specimen of this rock relatively poor in glass ana apandoned 
by sphaerules was analysed with the following results: 
| 3 A num- er- ; i “ | ae 
Mer Dt | Mineral composition („Nerm“) | of Osann 
| SiO, 2:51.60. 49.12 || O.860 57.281 ÖR NN 2.70 1s...579| 
Al,O, 1438911 l'3-62 |: 01146} CE ÖP ace Ne No 8.34 1 Arne 
Fe,0, | 4.32! 6.78 | 0.026 ‘uo pol ABs nes. 23.58) F DISSE NES 
PEO 960 MATS 0131 Ais i Aree ee test 23.91 WISE 
MgO | 6.09) 3.19} 0.152 | 10.12 | Serene Keio haa Ge 
| L 58.5: | 
_ CaO 6.77 | 8.70] 0.120} 7.99 | oH 2 la... 38 
| Na,O | 2.78) 2.49} 0.04) 2.99) Di sCaSiO, ... | LER 2:5 
K,O | 1.39} 1.26] 0.015 | 1.00 MgSiO, ... 4.06 PRATER 
H,Oat110° 0.87) fe  IMESIO, - al 2... 06 
0. y | 
H,O > 110? | 1.33 J DE — (FeSiO,. . . 12.67 |M.. 2.26 
| TiO, 0.00 0.80| 0.009, 0.60 | ME ........... 68 ay 7.es | 
P,O, aa a CO a Eee 1.375 | 
‚ MnO ee na Z fem 39.56 
| | | | DO een oer 0.03 
| | | | KON: 2.20 
100.27, 99.58, 100.00) 100.03 | 
We | Oo) 6 ie Magmatie symbol: Ul, 5, 3,4 | | 
| | Camptonose | 
1 A chemical analysis of the isolated sphaerules confirms the closeness of them 
to „hullite* as shown by the comparison tabulated as below: (next page) 
