The latest Wedding and Home Survey shows that the average cost of a diamond engagement ring is #328 while the most expensive ring in the survey cost #4,800. 
When choosing a diamond there are four aspects to take into account &dash. carat weight, clarity, colour and cut. 
Carat weight determines the size of the diamond with the word carat being <tag "515673">derived</> from carob as carob seeds were traditionally used to weigh the stones. 

