Some things can be a necessity of life, example, of poor Youyanjiangcu tea these things, the things essential to our everyday life, but something is not necessarily a life necessity, because of them we still livinggood, but people are often the pursuit of these are not necessities of things, such as diamonds, jewelry, furs, wait until these things, these things are more expensive, and to identify bad, so there are many institutions to identify these things true and false,For example, gia is the identification of the institutions of the diamond authenticity.