118 



i greenish. The enstatite is rare ; one crystal, -02 in length,, 

 ochroic a and j3 pale yellow-brown, y greenish-brown. Collected 

 i the west side of the lake before the eruption of 1886. 



(2) Highly vesicular, almost pumiceous, pale grey. Section : 

 Ground-mass very abundant, partly vitreous and partly crystallitic 

 and turbid : it contains many longulites and a few elongated 

 vesicles, but is not microvesicular like the last. The porphyritic 

 minerals are quartz, sanidine and plagioclase with a few small 

 fragments (-02) of brown hornblende. The quartz goes to -025 ;. 

 the sanidine to -06 ; and the plagioclase to -03. Magnetite is 

 rather plentiful ; Ilmenite occurs also. This specimen was thrown 

 out of Mt. Tarawera during the eruption of 1886 and was picked 

 up at Te Ariki, by the boat party on June 1 4th. It was very hot 

 when collected, four days after the eruption, and was roughly 

 rounded by attrition. 



Lake JRotorua^ Tauranga Co. — (a) Micro- vesicular variety. — A 

 white granular looking rock, with quartz, felspar, and magnetite, 

 but vesicular. Section : Ground-mass in small quantity, partly 

 crystallitic and partly pumiceous. The elongated vesicles start 

 from the porphyritic crystals and do not fold round them. In 

 places the ground-mass has become opaque white (kaolinised ?). 

 The porpheritic minerals are quartz, plagioclase, sanidine, and 

 magnetite with small quantities of greenish hornblende and biotite. 

 The crystals are crowded and reach -08 in length. The sanidine 

 is subordinate to the plagioclase. From Mokoia Island. Frag- 

 ments also occur, not uncommonly, in the cliffs of the lake at Te 

 Ngae. It is the ' Nevadite ' of Zirkel in the voyage of the Novara, 

 Geol. Vol. I., p. 110. 



(b) Spherulitic variety.— Grey, or pale brown, stony, often 

 banded, and with scattered quartz crystals. Spherulites sometimes 



Section, Ground-mass very abundant and generally banded lighter 

 and darker ; often irregularly stained with hematite or limonite : 

 the lighter portions with their long axes in the direction of the 

 coarser banding. With crossed nicols numerous incipient spheru- 

 lites, about -004 inch diameter, often appear; while in some there 

 are true spherulites from '06 to -08 in diometer. The porphyritic 

 minerals are quartz, sanidine, plagioclase and very dark hornblende. 

 The plagioclase and sanidine are about equal in quantity. Occur 

 as fragments in the cliffs at Te Ngae ; they are very various in 

 texture and cannot be described in a single paragraph. 



"amuri, E. I'au]>i> Co — Pale green rooks with fragments o 

 ; pumice, and scattered gU^sv crystals not \ery tonspicuou 

 } naked e>e Section Ground mass pirtly crystallitic an( 



