Pseudosecondary inclusions

Sometimes, fractures can be produced and subsequently healed during the same process of crystal growth. In this case, inclusions contained in healed fractures actually are primary inclusions too, by their time of formation and by the type of trapped fluid, corresponding to that responsible for the host crystal growth. Such inclusions are called pseudo-secondary because of their appearance in a form of veils, tracing healed fractures, typical for secondary inclusions discussed in the next section. But in fact they are just a specific type of primary inclusions; they have the same phase filling and value for studies of the host crystal formation conditions.

Differentiation of pseudo-secondary and secondary inclusions can be difficult, since their appearance is very similar. Only when a veil corresponding to a healed fracture is overgrown by the later layers of the same crystal, then one can be sure that such fracture was produced during crystal growth and not afterwards.

Plotting for typical location of a veil of pseudo-secondary inclusions in emerald crystal, crossing through early growth zones, but clearly overgrown by later layers of the same crystal. Brazilian emerald, immersion, field of view 4 mm.

 

Not all fluid inclusion assemblages in form of veils are generated as a result of fracture healing; they also can generate during the process of crystal growth, probably reflecting the location of some crystal structure defects in growing crystal. For example, in some synthetic analogues of natural gemstones, veils of inclusions also can be found, in spite of clear absence of any fracturing of growing crystals in these cases, in contrast to natural minerals that can be subject to mechanical deformations in the deposit. Veils formed by tiny flux inclusions are typical for flux-grown synthetic emerald, ruby and sapphire, spinel and alexandrite. Also, veils of fluid inclusions can be found in synthetic hydrothermal emeralds and quartzes.

Pseudo-secondary veils of solid and solid-gaseous inclusions in Russian synthetic flux-grown emerald. Field of view 1.2 mm.

 

Veils of fluid inclusions in synthetic hydrothermal emerald. Note also the growth structure characteristic for this synthetic material. Field of view 4 mm.