The sixth Mandala of the Rig Veda has 75 hymns, mainly to Agni and Indra. Most hymns in this book are attributed to the bārhaspatya family of Angirasas, especially to Bharadvaja. It is one of the "family books" (mandalas 2-7), the oldest core of the Rigveda.
Deities addressed besides Indra and Agni include the Vishvadevas, Pusan, the Asvins, Ushas (Dawn), the Maruts, Dyaus and Prthivi (Heaven and Earth), Savitar, Brhaspati and Soma-Rudra.
The rivers mentioned in the sixth Mandala are the Sarasvati, Yavyavati and Hariupiya. RV 6.61 is entirely dedicated to Sarasvati. In RV 6.45.31 the term Ganga occurs whichrefer to the River Ganges.
Talageri (2000), based on his proposition of an westward expansion early Rigvedic culture from Harayana (contrary to the nearly universally assumed eastward expansion from Gandhari) and his identification of some Rigvedic rivers, claims this Mandala as the oldest of the family books.
The dedication as given by Griffith is in square brackets