SANDSTONE AND SHALE

Major Rock Type: Sedimentary Rock
Lithology: Sandstone
Age: Oligocene – Early Miocene (33.9 – 15.97 million years ago)
Origin: Beaufort, Kota Kinabalu

* This is a compacted sandstone from Crocker Formation in Sabah, similar to the other sandstone samples from Croker Formation.

* The sample has very fine to fine grains of minerals, mostly accommodated by higher concentration of quartz.

* The grains shape is rounded to sub-rounded and the composition of the sandstone is almost similar to quartz arenite.

* All the sandstone from Crocker Fm. Might have gone through slight metamorphism due to emplacement of the Kinabalu igneous pluton.

* Spherical shape sandstone known as cannon ball which is medium to coarse grained is a unique geological process where mineral rich water seeps through the porous layers and act as a kind of glue, holding these sediments together, often forming around a core. As more and more layers are deposited, the concretion builds outward like a pearl, before being exposed by erosion.