This refers to the transparency of a gemstone.
At first you may feel that diaphaneity (transparency) should really be covered under the heading of clarity, however a transparent gemstone may sometimes lack good clarity, even when no inclusions are noticeable. As you will read under several headings in this book, I believe you should not use a loupe with coloured gemstones and only use them for diamonds, which due to the introduction of the GIA grading system make a big thing about clarity and therefore infers that inclusions make a natural gemstone somehow substandard.
So, if you no longer use a loupe to measure gemstones and judge clarity with the naked eye as you should, you now need to introduce a new valuation criterion to your methodology. We are now going to start thinking about transparency, or if you want to sound like a real expert - diaphaneity.
As most organic gemstones like Amber, Jet, Pearls etc aren’t transparent, I am going to refer a lot in this section to crystals. After all, with the exception of amorphous gemstones, all others have a crystal structure and you will often hear the phrase “crystal clear”. What does this phrase mean? Complete transparency, or technically speaking, diaphaneity.
In older gem books that I have read, you won’t see the words crystal clear or diaphaneity, but many references to water. Quality gems with good transparency were called “first water” gems and then second, third and fourth water gems would follow. If a gem had poor transparency, lacked vivid colours etc, then they would call it a “bye water” gem.
So clarity refers to whether you can see inclusions or not, whilst transparency refers to how clear the gem is: is it like looking through glass or is it hazy, foggy, sleepy, murky, cloudy? Even in 400BC, early Indian writings list the qualities of a gemstone by saying “it should be transparent and reflecting light from inside” (Rangarajan, ‘The Arthashastra’).
Even when we see inclusions we should still consider the gem’s transparency. Take Zambian Emeralds, even the very finest pieces are likely to still have some inclusions, however what sets Zambian Emeralds apart from others is often their transparency. Does the gem look like green grass, or is it cloudy? What would you prefer, a cloudy Emerald with just a couple of inclusions or a transparent Emerald, one more like glass, but with more inclusions? You see it’s not normally the inclusions you see with your eyes that kill the life of a gem, but the little tiny fibrous ones that you can’t see that form clouds and render the gem sleepy. As far as I am concerned, transparency normally plays a far more crucial role in evaluating gemstones than inclusions.
