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Petrography. — 11 On Micaleucite basalt from Eastern Borneo” By 
H. A. Brouwer. (Communicated by Prof. G. A. F. Molengraaff.) 
The occurrence of leucite rocks in our East-Indian Archipelago, 
at the same time the first occurrence outside Europe, was observed 
by Vogelsang from the Gunung Bantal Susum on the island Bawean; 
Vogelsang’s observations were described after his death by Zirkel *) 
in 1875. 
Lofftf *) described leucite rocks from Java from the Gunung Ringgit, 
an extinct volcano on the north coast of the residence Besuki, and 
Verbeek *) from the Gunung Muria and the mountain Patti-Ajam 
in the residency Djapara. Behrens * 2 * 4 * ) described rocks from the same 
localities. 
In Celebes Wichmann 6 ) discovered in 1888 leucite basalt in the 
southwestern peninsula among the boulders of the river Pangkadjene, 
and leucitites from the rivers Masepe (near the kampong of the same 
name) and Walannae, a tributary of the Minralang (upper course-of 
the Tjenrana). Retgers 8 ) mentions leucitites from Malawa (Mountain 
Regencies, northern district, South Celebes) and finally Bucking biotite 
leucite basalt, underlying limestone with Nummulites east of Kantisang 
near Bangkang Sakiang 7 ), leucite basalt near Tandjing Lossa on the 
Mandar coast (lat. 2°42' south) and leucitites in conglomerates near 
the kampong Tambi in the bay of Manudju 8 ). 
From Borneo no leucite rocks were hitherto known. 
Now Prof. Molengraaff recently discovered among the collection 
of rocks, made by Prof. Nieuwenhuis in the basins of theMahakam 
and the Kajan in Eastern Borneo in the years 1896—’97 and 
1898—1900, a leucite rock, which he placed at my disposal for 
further investigation. 
*) F. Zirkel, Neues Jahrbuch f. Mineral. 1875, biz. 175. 
2 ) J. Lorie, Bijdrage tot de kennis der Javaansche Eruptiefgesteenten. Dissertation, 
p. 247. Utrecht, 1879. 
s ) R. D. M. Verbeek und R. Fennema, Neue Geologische Entdeckungen auf Java. 
Neues Jahrb. f. Mineral. BB. 2. 1883, p. 205. 
4 ) H. Behrens, Beitrage zur Petrographie des Indischen Archipels. II. Verh. K. 
Ak. v. W. Amsterkam. XXXIII. 1883. 
6 ) A. Wichmann, Leucitgesteine von der Insel Celebes. Petrogr. Studien fiber en 
Indischen Archipel. I. Natuurk. Tijdschr. v. Ned. Indie. LIII. 8. 1893. 
®) J. Retgers, Jaarb. v. h. Mijnw. in Ned. Oost-Indie, 1895, p. 99. 
7 ) H. Bucking, Leucitbasalt aus der Gegend von PandkadjenS in Sud*Cele es. 
Ber. Naturf. Ges. Freiburg i. B. 1899, XI, p. 99. 
8 ) H. BCcking, Beitrage zur Geologie von Celebes. Sammlungen des Geologise en 
Reiehsmuseums in Leiden. VII, 1902—1904, p. 43. 
