1 Mukhi Rudraksha as per various Puranas :
The One Mukhi Rudraksha is the symbol of Godhood, Supreme Truth and Attainment of Eternity. The One Mukhi Rudraksha is itself Lord Shankar and it is the main among all Rudraksha of all faces. It is ruled by the Sun and enlightens the Super Consciousness. It brings the power of Dharana to the wearer meaning the power to concentrate the mind on an object. The wearer of One Mukhi Rudraksha gets his mental structure changed and he begins to feel renunciation from the worldly affairs and naturally inclines towards GOD. His mind begins to concentrate on the Supreme Element that is Partattva Dharana cha jayate Tatprakashnam thus the discoverers of Aatma Tattva must wear One Mukhi Rudraksha.
This is the best of all Rudrakshas. Peace and pleasure abide in the house where One Mukhi Rudraksha is worshipped. The person who worships it obtains not only all the worldly pleasures during his life span but also remains unaffected by them. It is ideal for Doctors.
In the Srimaddevibhagavat 11th Skand Chapter V verses 25 and 26 it is stated "According to Jabala instinct for wearing Rudraksha results only after attaining the perfection of Vedas and blessings of Lord Siva during preceding births". In Chapter VII verse 23 it is stated "Rudrakshas infused with Bija mantras should be worn. One Mukhi Rudraksha helps envisioning the Partattva". In Padma Purana Chapter 57 Translated by Bhatta 1989 it is stated in verse 38 to 39 "The Rudraksha of one mouth is virtually Siva, it removes the sin of brahmanacide. Therefore one should wear it for the destruction of all (ones) sins. He would go to Siva's heaven and rejoice with Siva. O Kartikeya a man would obtain a Rudraksha of one mouth due to great religious merit and due to Siva's favour and would also obtain Kailasa".
One Mukhi Rudraksha is found in two shapes round and the half moon shape. Round Rudraksha is highly praised in our ancients texts but it is very rare and more of a myth . One Mukhi Half moon is easily available and found in a family tree of Rudraksha from India and Srilanka.From the point of view of importance there is no difference between them. Therefore it must be real and pure in whatever shape it may be. The cost of One Mukhi Round is more than the half moon shaped Rudraksha.