Not all sellers provide diamond grading lab reports (aka diamond quality reports) to their consumers. So my general advice to you is to keep your money in your pocket when dealing with such jewelers.

Only purchase a diamond engagement ring if it comes with the original diamond quality report.

A lab report is an independent evaluation of the 4Cs of a loose diamond and includes a plotted diagram of the stone's clarity characteristics and a graphic representation of the stone's proportions. Having such a report allows you to compare diamonds of different qualities and ultimately helps you make a more informed buying decision.

A retailer may cut corners and not provide a lab report or an unscrupulous seller may provide a fake one because of the time, trouble and expense he'll bear to getting a stone graded.

Yeah - there is a price for grading a diamond (though that cost is eventually paid by the consumer), plus the shipping and insurance charges for sending the diamond to the lab. And let us not forget the opportunity cost of a jeweler not having the diamond in his store for sale for a few weeks while the grading takes place.

However, a diamond grading report may also not be available  buy fake diploma because the costs to getting one may impact too heavily on the final price of the ring.

For example, a 0.3ct diamond ring costing $250 say, may cost around $75 to be graded and have the report number inscribed on the girdle on the diamond.

As you search for that ideal diamond engagement ring for your sweetheart, you'll find that there is an alphabet soup of labs claiming to provide reputable diamond grading reports. But I would only put my money on...

The Premier Diamond Grading Lab Reports

Yes, all diamond quality reports are not created equal. Within the industry, it is a consensus that the two premier labs are GIA-GTL (Gemological Institute of America's Gem Trade Lab) and the AGS (American Gem Society Laboratories).

The GCAL (Gem Certification and Assurance Lab) also offers highly regarded reports or "diamond certificates" as they are referred to by GCAL.

The GIA has the strongest global reputation for independence and consistency. Due to their constant color and clarity strictness guidelines, the globe's largest and most expensive diamonds have been sent there for grading decades. In 2006, GIA-GTL added a two-dimensional cut grading system for round brilliant diamonds.

AGS uses the strictest cut standards in the industry. It uses a three-dimensional light performance metric that can grade several diamond shapes. In fact, it is the only cut grading system that is recognized by the scientific community.

What is more, its Diamond Quality Document uses a unique and proprietary 0 to 10 grading system to evaluate the 4 Cs - a system which is easier to comprehend than GIA's grading system. In fact, AGS even goes the extra step by equating their 0-10 rating scale to other forms of rating.

For example, the conventional VS1 diamond clarity rating is a 3 on the AGS Diamond Quality Document.

Diamond Reporting - The Drawbacks

1. Diamond grading is not standardized or regulated and hence you may come across tier 2 labs that employ looser guidelines to the tier 1 grading labs mentioned above.

If you buy a diamond that has been graded by a tier 2 lab, you may end up paying more for a lesser quality diamond. So for example, a diamond rated a "F" in color at a tier 2 lab may get a G, H, or lower color rating at a more reputable lab.

The industry also discounts diamonds graded by lesser known labs by about 15-30% or more. So either you only buy a diamond graded by a tier 1 lab or you accept that you might be buying a lesser quality diamond than what is stated on the report if that diamond is graded by a lesser known lab.

2. Many large chain stores have huge contracts with lesser known labs with "softer" diamond grading guidelines. Some of these softer labs put "suggested replacement values" on the lab reports - values which are higher than what stores intends sell the diamonds for.

So a salesperson in a chain store may say to you, "Look at the great deal you are getting here. We are selling you this diamond engagement ring for $2500 but the report says that the suggested replacement value is $4000." Wow - what a deal - NOT! This is why it is better that you trust only independent tier 1 labs.

Also bear in mind that reputable diamond grading reports are not appraisals and don't offer appraisal figures. Diamond appraisals are often grossly inflated and are not something you'll want to rely on.

3. Diamond reports are riddled with disclaimers that specify that nothing is "certified" or guaranteed and that the labs are not accountable for errors. In fact, the GIA offers a disclaimer of sorts on their website regarding the use of the word "certify." The website says:

"It is incorrect to state that students, graduates, their businesses, or particular gemstones are "certified" by GIA. The Gemological Institute of America does not certify anyone or anything. Neither a student nor a graduate who has been awarded a certificate or diploma, nor a gem which has been graded or identified by GIA has been certified by GIA".

So it is possible that you the consumer is left holding the bag should an inaccuracy in a report is later discovered. Courts have frequently ruled that sellers, not labs, are responsible for such errors. Why? Because the labs indicated beforehand that their reports couldn't be held liable.