Gemstone inclusions can be defined as a material that is trapped inside a mineral while that mineral is forming. The question we most commonly get asked, however, is “how” does it occur?
There are basically three ways inclusions can end up inside a crystal or stone.
1. Protogenetic – This is characterized as when the stone/crystal formed before the quartz inclusion, and thus as the crystal/stone grows it simply engulfs the mineral quartz formation, and does not really interrupt or change the inclusion in any way. These are commonly observed as fibers that seem to be running through the entire stone/crystal all over it in different arrangements. Rutilated Quartz and Tourmalinated Quartz tumbles are excellent examples of this process.
2. Syngenetic – This occurs when both the quartz inclusions and the stone/crystal are growing at the same time. This does tend to disrupt the shape of the inclusion. Sometimes the crystals are altered so much during the process that the stone is hard for geologists to identify. In some cases, this process produces phantom inclusions. Excellent examples can be seen in green and red phantom quartz specimen, as well as scenic quartz.
3. Exsolution – This final style of quartz inclusion formation is characterized by changes in temperature or pressure during the growth period of the crystal/stone that made is possible for a quartz inclusion to penetrate the crystal lattice of that stone, an event that would not normally be possible, but that under a particular set of conditions, was able to occur. The actual inclusions are referred to as epigenetic, and usually result in the stone/crystal creating a new, separate crystal lattice, and technically becoming a different mineral. Rose quartz is an excellent example of this process.
Scientists enjoy working with quartz inclusions, as they do not tend to alter the mineral composition of stones too greatly, which allows for better identification of the mineral being studied. In some cases, the presence of quartz inclusions have made it possible for scientists to estimate the actual temperature in which a crystal formed. Some geologists have referred to quartz inclusions as a “window to the past” and one in which they are able to derive a good deal of information that they may not have been able to.