Clarity is measured visually and according to standards.
You can review the guidelines, below.
If by 'you' you mean 'U', and you're query is about clarity and not colour, it is possible that 'U' indicates unenhanced. Unenhanced diamonds are more valuable than enhanced diamonds.
Not all diamonds are clear. Take your diamond to a jewelery store or a gemologist and ask for an evaluation of your diamonds. The lack of clarity can affect its value.
The initial J refers to colour, not clarity. On the scale of colourless diamonds, J fits into the range of slightly yellow.
Your question includes two characters:H is used to describe a colour of a 'white' diamond, and indicates that the diamond is barely yellow1 must be preceded by other letters in order to signify clarity. Those letters can be VVS, VS, or I.
That depends, some gems are being made now to look almost completely like the real thing. However these are marked specifically because they are so hard to tell from natural diamonds. However, cheap diamonds that are crystal or glass will be obvious form the naked eye due to the clarity, and color.
Diamonds are measured by carat weight, clarity, colour and excellence of the cut, some of which are named.
The clarity of the response required no further inquiry. Diamonds and wine are judged by their clarity.
Clarity is relative, some diamonds are hardly clear at all.
Diamonds are rated according to the colour, clarity, carat weight and cut.
Cut diamonds are valued by their cut, clarity, carat weight and colour.
Diamonds are weighed in carats. Diamond colour is measured in a specific diamond colour, from D to Z, D being colourless and Z being quite -- but not fancy color -- yellow. There are 27 colours of colored diamond, measured in saturation, from faint to vivid. Diamond clarity is measured by inclusions, from I -- included to FL -- flawless.
If by 'you' you mean 'U', and you're query is about clarity and not colour, it is possible that 'U' indicates unenhanced. Unenhanced diamonds are more valuable than enhanced diamonds.
IMP1 is not an acronym commonly association with diamonds.
Clarity enhanced diamonds are real, mined diamonds that have had their clarity/quality improved by cleaning and cloaking any visible imperfections in the diamond. Clarity enhanced diamonds are lower in price than 100% natural diamonds and therefore for every given carat weight and quality, the price will be lower. Clarity enhanced diamonds are graded after the enhancement and therefore if the diamond was originally F/SI1 and is now F/VS2, it will be priced lower as if it were still F/SI1, however will look like F/VS2. (see related link)
Debeers diamonds are the standard by which most diamonds are measured.
Diamonds are valued by cut, colour, clarity and colour. Without those details, pricing 19 diamonds is not possible.
Diamonds are graded according to clarity, colour, cut and carat weight, basically in that order of priority.