We present the discovery of five new quasars at z > 5.7 , selected from the multicolor imaging data of the Sloan Digital Sky Survey ( SDSS ) .
Three of them , at redshifts 5.93 , 6.07 , and 6.22 , were selected from \sim 1700 deg ^ { 2 } of new SDSS Main Survey imaging in the Northern Galactic Cap .
An additional quasar , at redshift 5.85 , was discovered by coadding the data obtained in the Fall Equatorial Stripe in the SDSS Southern Survey Region .
The fifth object , at redshift 5.80 , is selected from a non-standard SDSS scan in the Southern Galactic Cap outside the Main Survey area .
The spectrum of SDSS J162331.81+311200.5 ( z = 6.22 ) shows a complete Gunn-Peterson trough at z _ { abs } > 5.95 , similar to the troughs detected in other three z \mathrel { \hbox { \hbox to 0.0 pt { \hbox { \lower 4.0 pt \hbox { $ \sim$ } } } \hbox { $ > $ } } } 6.2 quasars known .
We present a composite spectrum of the z > 5.7 quasars discovered in the SDSS to date .
The average emission line and continuum properties of z \sim 6 quasars exhibit no significant evolution compared to those at low redshift .
Using a complete sample of nine z > 5.7 quasars , we find that the density of quasars with M _ { 1450 } < -26.7 
at z \sim 6 is ( 6 \pm 2 ) \times 10 ^ { -10 } Mpc ^ { -3 } 
( H _ { 0 } = 65 km s ^ { -1 } Mpc ^ { -1 } , \Omega = 0.35 and \Lambda = 0.65 ) , consistent with our previous estimates .
The luminosity distribution of the sample is fit with a power law luminosity function \Psi ( L ) \propto L ^ { -3.2 \pm 0.7 } , somewhat steeper than but consistent with our previous estimates .