 Geologists also define the High Himalayan Crystalline rocks extending 150 kilometers from the Main Central Thrust to Tethys Ocean sediments in the north.Sillimanite, garnet and biotite are especially common in this area.The Takhtsang monastery, carved into Takhtsang gneiss, is surrounded by rocks with calcsilicate lenses, interpreted as the "hand and foot prints" of Padmasambhva—an important founder of Bhutanese holy sites.