Because of the Qomolongma detachment. This is a band where the limestone on top has moved relative to the metamorphic rocks underneath. Mountains are build by a combination of uplift, stretching, moving and folding of rocks. read more
There is limestone at the top of Mount Everest because the collision of the India plate with the Eurasian plate sandwiched the former sea floor of the Tethys Sea; all the marine sediment (from which limestone is formed) was thrust upwards to become the bulk of the Himalayas. read more
The Qomolangma Formation, the highest section of rock on the summit pyramid of Mount Everest, is made of layers of Ordovician-age limestone, recrystallized dolomite, siltstone, and laminae. The formation starts about 5.3 miles up the mountain at a fault zone above the North Col Formation, and ends at the summit. read more
The middle part of Mount Everest is known as the North Col Formation, 7,000 to 8,600 meters. This section, itself, can be divided into different parts, the top 400 meters, named the ‘Yellow Band’, is formed from linked beds of a brown, Middle Cambrian, marble (diopside-epidote-bearing), muscovite-biotite phyllite (which contain silicate minerals) and semischist (a partly metamorphosed, layered sedimentary rock). read more