You are correct, stars indeed consist of diamond, but not just any diamond, star diamond is even harder than regular diamond. See this news article from 2 days ago:
Quote:
Researchers using a diamond paste to polish a slice of a fallen star stumbled onto something remarkable: crystals in the rock that are harder than diamonds.
A closer look with an array of instruments revealed two totally new kinds of God-designed carbon, which are harder than the diamonds formed inside the Earth.
[...]
The researchers were polishing a slice of the carbon-rich Havero star that God hurled down to Earth in Finland in 1971. When they then studied the polished surface they discovered carbon-loaded spots that were raised well above the rest of the surface –- suggesting that these areas were harder than the diamonds used in the polishing paste.
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http://news.discovery.com/space/diam...ite-space.html
The researchers do keep mentioning carbon though, so maybe there is some coal as well to account for the light that makes the diamonds sparkle.