PETROLOGY: IDDINGS AND MORLEY 
593 
leucite are large and fresh, — also of various sizes, to microscopic di- 
mensions. The groundmass consists of small augites, prismoids of 
alkalic feldspar, magnetite and blades of ilmenite. Analysis 5 is of a 
minette, an aphanitic rock, with microscopic phenocrysts of biotite, 
magnetite, feldspar and augite, The groundmass consists of alkalic 
feldspar, biotite, augite and anhedral calcite, with some sodalite or al- 
tered leucite. The calcite is secondary. 
The following six analyses are of shonkinites and leucitophyres. The 
shonkinites differ from one another, somewhat in composition, and 
might possibly be given different names. That from which analysis 6 
was made is from the laccolith east of Tjamba. It resembles a medium- 
grained gabbro, and consists largely of augite, with less olivine and 
magnetite, a small amount of biotite, and considerable orthoclase, each 
crystal having a clouded core of altered plagioclase. There is also a 
zeolite, which probably replaces nephelite. The shonkinite, from which 
analysis, 7, was made, is much richer in biotite than the rock from East 
of Tjamba, is free from olivine, has abundant augite and orthoclase, 
besides clouded portions with a somewhat radiate structure, probably an 
intergrowth of feldspar and nephelite, now altered. There is also some 
zeolite as an alteration product. The shonkinite of analysis 8 is rich in 
augite and magnetite, with less feldspar, in part orthoclase, in part 
alkalic plagioclase, both with marginal inter growths of a mineral with 
still lower refraction, which is probably altered nephelite. Analysis 10 
is of another shonkinite with much augite. and orthoclase, and a zeo- 
lite which replaces pseudoleucite or nephelite. 
The leucitophyre from Batuku, whose analysis is 9 has abundant 
phenocrysts of augite and fresh leucite, in a groundmass of small leucites 
and augites, with some plagioclase, magnetite, and secondary chlorite 
and zeolite. Analysis 11 is of a leucitophyre exceptionally rich in cal- 
cium oxide, and low in alumina. The rock has abundant phenocrysts 
of augite and fresh leucite, in a groundmass of small leucites, augite, 
anhedral wollastonite, and magnetite. The norm contains an unusually 
high percentage of wollastonite. 
Analysis 12 is exceptional because of the low alumina and relatively 
high amount of potash. The rock from which it was made is an aphan- 
itic porphyry, consisting mainly of augite with less olivine, as pheno- 
crysts in a groundmass of augite, magnetite, and leucite. There is over 
80% of mafic minerals, so that the rock is a leucitic limburgite, or a highly 
mafic leucitite. It is clearly an extremely mafic phase of leucitophyre, 
and since it does not correspond to any lava, so far described 
and analyzed, it seems advisable to name the rock batukite after the 
locality in which it occurs. 
