Please do not write 'Original ground has one grain to dress up well already the diamond' in your 作文 because your teacher will laugh at you....I am really sure that he used an internet translater
If I were you, I will use the following sentence
'Wow, there is a very unbelievably shiny diamond on the floor'
or
'Wow, there is a beautiful diamond on the floor, how come I didn't see it'
It is quite hard to write 原來 in English, so I suggest to use the second sentence
'Wow, there is a beautiful diamond on the floor, how come I didn't see it'