In the 1700s, Lavoisier proved that diamonds are carbon only, by burning one and analysing the gas to show that it was CO2. Therefore the diamond was carbon. Yellow diamonds have a contamination of...
The phrase "diamond accents" in the description of a piece of jewelery generally refers to small diamonds. Often they're so small you'd need a magnifying glass to tell that they actually are there.
Generally speaking, manufactured diamonds have the same chemical and physical properties of diamonds which are dug from the earth. So, yes, they are real. A certified gemologist will be able to...