Рет қаралды 13,389
Most gems form naturally as minerals within the Earth. Most form as crystals, solids whose atoms are arranged in highly ordered repeating patterns called crystal systems. Learning about mineral crystallization and the geological processes involved in gem formation will help gemologists understand some of the properties they’ll encounter in gemstones.
Crystal Specimens Composed of Different Minerals
Even if a closed passage reopens and fluid again enters a cavity, a totally different mineral may crystallize over the existing material. Indeed, temperature, pressure, and the chemistry of the fluid solution often vary over time. Different conditions will produce different mineral crystals within a cavity. When opening a deposit, you’ll commonly see different minerals covering earlier layers.
Inclusions
Such changes of conditions within a cavity is also one cause of gemstone inclusions. A new crystal may start to grow on an older and larger one, only to have its growth process stop. If conditions that allow the original crystal to grow resume, the older crystal will grow over the newer one.
#AndrewPidor