An emerald is as green as grass;
A ruby red as blood;
A sapphire shines as blue as heaven;
A flint lies in the mud.
A diamond is a brilliant stone,
To catch the world's desire;
An opal holds a fiery spark;
But a flint holds fire.
Christina Georgina Rossetti
http://www.poemhunter.com/poem/an-emerald-is-as-green-as-grass/
