Internal Diamond Flaws
Being a natural formed substance, diamonds have gone through a lot of stress in the creation process, and no two are exactly the same. Most diamonds do have flaws because for some reason it did not form correctly. Most of these inclusions, or internal flaws are not seen by the naked eye and may not be that important unless they threaten the structure of the diamond.
Very few diamonds are labeled as perfect, but those that are will in all probability be extremely valuable, and therefore expensive.
Some more minor inclusions may cause a diamond to appear somewhat dull. An inclusion within a diamond may affect the clarity of the stone. This occurs when as light passes through the stone, it is interrupted by the inclusion. A number of these inclusions and flaws can be repaired or reduced by various forms of treatment that jewelers and gemologists have become skilled in over time.
Some diamond inclusions or flaws may be large enough to threaten the structure of the gem, and allow it to shatter or break far more easily than a stone without this weakness. These are serious flaws and greatly reduce the value of your stone.
A diamond that has speckles or dark crystal in clusters or distributed throughout the stone, is considered to have a type of diamond inclusions and flaws referred to as pinpoint inclusions. When the dark crystals are gathered together in the stone, the clarity of the diamond is influenced, and it appears there is a “cloud” inside the stone. These diamond flaws and inclusions may give the diamond less value, as it greatly effects it's appearance.
Problems from Laser Treatments
When a diamond imperfection is treated with lasers to remove dark diamond inclusions and flaws within the gemstone, many times a line can be left through the diamond that appears much like a thread. This laser line starts at the outer edge of the diamond, and moves within the stone to the area where the dark inclusion was treated by the laser. These inclusions and flaws are unattractive and can usually be easily spotted by most people, which makes for a less desirable diamond.
Mineral and Crystal Inclusions
Many diamond inclusions and flaws are considered to be negative, but there are situations when some flaws and inclusions are actually an appealing aspect of a diamond. As an example , diamonds typically have smaller crystals inside the diamond, often so small they are not seen without some type of a magnifying device. The clarity of the stone can be influenced by these small crystals. This occurs when there are a number of them and when they are all grouped together in one area of the diamond.
There have been rare instances when another gem stone is actually inside a diamond, and certainly would not be viewed as a diamond flaw or inclusion. There are occurrences of diamonds containing other gemstones within them such as a garnet, another diamond, or another mineral substance.
Illa Maden gives more facts and interesting info on precious gemstones and also find a birthstone list .