Shompole Volcano, Kajiado County, Kenya

Melanite garnet, with dodecahedra modified by smaller trapezohedron faces, exposed on an ijolite xenolith in nephelinite lava. The melanite was surrounded by soft minerals (zeolites, clay, and carbonate) which were weakened by dilute hydrochloric acid, then abraded away.

© Tony Peterson

Thin section photomicrograph (plane polarized light) of a nepheline phonolite from the lower west slopes of Shombole volcano. Flow-oriented phenocrysts of green aegirine separate large, euhedral nepheline, wedge-shaped titanite, and a few dark brown melanite crystals. Small needles of sanidine are in the groundmass.

© Tony Peterson

FOV=4 cm. Melanite garnet, with dodecahedra modified by smaller trapezohedron faces, exposed on an ijolite xenolith in nephelinite lava. The melanite was surrounded by soft minerals (zeolites, clay, and carbonate) which were weakened by dilute hydrochloric acid, then abraded away. One stereo image in this series. Collection and photo, T. Peterson.

© Tony Peterson

FOV=1.7 cm. Stereo pair. Melanite garnet, with dodecahedra modified by smaller trapezohedron faces, exposed on an ijolite xenolith in nephelinite lava. The melanite was surrounded by soft minerals (zeolites, clay, and carbonate) which were weakened by dilute hydrochloric acid, then abraded away. Collection and photo, T. Peterson.

© Tony Peterson

FOV=2 cm. Melanite garnet, with dodecahedra modified by smaller trapezohedron faces, exposed on an ijolite xenolith in nephelinite lava. The melanite was surrounded by soft minerals (zeolites, clay, and carbonate) which were weakened by dilute hydrochloric acid, then abraded away. One stereo image in this series. Collection and photo, T. Peterson.

© Tony Peterson

Thin section photomicrograph (plane polarized light) of a nepheline phonolite from the lower west slopes of Shombole volcano. Flow-oriented phenocrysts of green aegirine separate large, euhedral nepheline, wedge-shaped titanite, and a few dark brown melanite crystals. Small needles of sanidine are in the groundmass.

© Tony Peterson

Crossed-polars version of the parent photo. Thin section of a nepheline phonolite from the lower west slopes of Shombole volcano. Flow-oriented phenocrysts of green aegirine separate large, euhedral nepheline, wedge-shaped titanite, and a few dark brown melanite crystals. Small needles of sanidine are in the groundmass.

© Tony Peterson

Thin section photomicrograph (plane polarized light) of a nepheline phonolite from the lower west slopes of Shombole volcano. Flow-oriented phenocrysts of green aegirine separate large, euhedral nepheline, wedge-shaped titanite, and a few dark brown melanite crystals. Small needles of sanidine are in the groundmass.

© Tony Peterson

Cross-polars version of the previous image. Thin section photomicrograph of a nepheline phonolite from the lower west slopes of Shombole volcano. Flow-oriented phenocrysts of green aegirine separate large, euhedral nepheline, wedge-shaped titanite, and a few dark brown melanite crystals. Small needles of sanidine are in the groundmass.

© Tony Peterson

Clasts of nephelinite lava and ijolite in a matrix of mud and/or ash, Shombole volcano. July 1985 photo.

© Tony Peterson

Late phonolite cones on the west flank of Shombole volcano. The north end of Lake Natron and the western wall of the rift valley (Nguruman Escarpment) are to the left. The bare brown areas are abandoned Masai campsites. Digitized 1986 transparency.

© Tony Peterson

A thin dyke of carbonatite (melanite-bearing sövite) running approximately north, parallel to a ridge on the north side of Shombole volcano. Hammer for scale. July 1985 photo, Tony Peterson.

© Tony Peterson

This border marker between Kenya and Tanzania, laid in March of 1934, was encountered about 300 metres up a ridge on the west side of the volcano. Digitized 1986 transparency.

© Tony Peterson

Nephelinite lava breccia in carbonatite at the foot of Shombole volcano, SW quadrant. Kenya shilling for scale. July 1986 photo, Tony Peterson.

© Tony Peterson

Photo of Shombole, about 50 km distant, looking south across Lake Magadi. Note the prominent valley between the peaks, which is a deeply eroded N-S normal fault. July 1986 photo by Tony Peterson. I listened carefully to the pronunciation of the local Masai, as Shombole is variably spelled with a b or a p in maps and publications. I determined ...

© Tony Peterson

Young Masai boys, who mind the herds of goats and cattle, are probably the hardest-working members of their society. Masai living around Shombole have a very traditional lifestyle and are not like their rich cousins living in areas frequented by tourists. Digitized July 1986 transparency.

© Tony Peterson

View looking west across the normal fault which cuts the east flank of Shombole volcano. Note layered lava flows/agglomerates. July 1985 photo, Tony Peterson.

© Tony Peterson

A view of the heavily eroded north slopes of Shombole, showing the layers of nephelinite lava flows and coarse clastic rocks (agglomerates and debris flows). Digitized July 1985 35 mm transparency. The reader may have noted that I spelled the mountain with a "b", but the Mindat locality description uses a "p", following present-day maps ...

© Tony Peterson