Geochemical studies of upper mantle rocks (peridotites) provide insights into the Earth's upper mantle evolution from the Archean to the present. This is because mantle processes play a key role in the formation of continents and largely assign geochemical properties of the Earth's crust. This book represents geochemical study of upper mantle rocks at two sites from different geological settings of the Bohemian Massif (Czech Republic) - Kozákov and Horní Bory. These localities were chosen as unique mantle suites, which could provide insights into the upper mantle processes (mantle depletion, metasomatism, melt-rock reactions) and behaviour of trace and highly siderophile elements in the upper mantle. Therefore, this book is of a broad relevance to all people involved in the Earth's upper mantle.