12 Technical Terms for Describing Loose Diamond Quality

As a diamond buyer, you are always looking for the best price. That price is determined by the quality, and the quality is determined by several important traits in the diamond.

In the industry, we use a number of terms to describe those traits, some of which may be unfamiliar. To get the diamond you want, you’ll want to make sure you understand these terms that describe a stone.

Diamond dealers analyse the traits of each precious jewel before deciding on its value, considering its colour, weight, transparency, marks, and cutting.

The difference between high-quality and low-quality loose diamonds can be enormous, and the best way to understand this gulf is by understanding the different kinds of stones available, and the unfamiliar terms that diamond dealers may use to define them. We want you to understand exactly what you are buying, so wouldn’t it be helpful if you had a guide to the kind of language that dealers are likely to use?

We certainly HOPE that it will be helpful, because here is that very guide!

Welcome to our glossary of some common diamond industry terms used by diamond dealers, after they have analysed the value of a certified or uncertified stone.

Common Industry Terms

BGM – A relatively new term that means whether the stone is Brown, Green or Milky. Brown and milky stones are considered less desirable than yellow ones, and green can (but doesn’t always) indicate that the stone was mined in Zimbabwe. This makes such stones very undesirable, due to controversies that surround diamond mining in Zimbabwe.

Inclusion – A small imperfection found inside a diamond.

Eye Clean – This means there are no inclusions visible to the naked eye.

Feather/Gletz – A type of inclusion: a crack that looks like a feather. It can also indicate a possible weakness if it occurs along the cleavage grain.

Grain/Grainer – An old-fashioned term for weight that remains in use. One grain equals 25pts, or a quarter of a carat; therefore, a 4 grainer is a 1ct stone. It is used more commonly with bigger stones – for example, +/- 1.25ct stones are commonly referred to as “5 grainers”.

Make – Refers to the overall appearance of the cut of a stone. It is not so specific as to assign a Cut grade; rather, it is to say a stone generally has a “nice make” or “poor make”.

Milky/Hazy/Sleepy – Describes a stone that has reduced transparency, often due to many microscopic white inclusions or occasionally very strong fluorescence.

Natural – A remnant of the surface of the rough crystal left on the polished stone, usually on the girdle. Naturals are very common and indicate that the cutter achieved the highest possible yield from the rough.

Indented Natural – As above, but the natural is big enough to visibly enter the stone. Often appears as a chip on the girdle.

Pique – Pronounced “pee-kay”, this old French term means “pricked”. It usually describes small marks, i.e. “spread black/white pique”, and is also used in Europe to mean I1, I2 & I3 on the GIA clarity scale. Therefore, P1, P2 & P3 are the equivalent grades.

TTLB/TLB – An acronym meaning Top Top Light Brown/Top Light Brown. It refers to the shade of the body colour of the stone, which is commonly either brown or yellow. As a general rule, a TTLB stone can be no higher than I colour, and is often graded below that.

TTLC/TLC – As above, except the body colour is yellow. The C means Cape, which is an old-fashioned, pre-GIA term for this colour.

Understanding how a loose diamond is valued

Armed with these phrases and acronyms, you will now be more aware of the most important points considered by dealers when assessing a loose diamond’s value. We hope that the terminology that you are better prepared to discuss the kinds of stones you are most interested in.

If you would like to see our database of certified and uncertified loose stones that Clark Diamonds can offer, sign up for our web app using the link below. We would also love to hear from you.

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