We present a metallicity distribution based on photometry and spectra for 442 \omega Centauri cluster members that lie at the main sequence turnoff region of the color-magnitude diagram .
This distribution is similar to that found for the red giant branch .
The distribution shows a sharp rise to a mean of [ Fe/H ] = –1.7 with a long tail to higher metallicities .
Ages have then been determined for the stars using theoretical isochrones enabling the construction of an age-metallicity diagram .
Interpretation of this diagram is complicated by the correlation of the errors in the metallicities and ages .
Nevertheless , after extensive Monte-Carlo simulations , we conclude that our data show that the formation of the cluster took place over an extended period of time : the most metal-rich stars in our sample ( [ Fe/H ] \approx –0.6 ) are younger by 2–4 Gyrs than the most metal-poor population .