The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula BeAl2O4.
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The name of the stone comes from the Greek words chrysos and beryllos. Meaning “a gold-white spar”. Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones. Although they both contain beryllium. The crystal is the third-hardest frequently encountered natural gemstone. And lies at 8.5 on the Mohs scale of mineral hardness.
Ordinary stone is yellowish-green and transparent to translucent. When the mineral exhibits good pale green to yellow color and is transparent, then it consider as a gemstone quality. The three main varieties of are: ordinary yellow-to-green chrysoberyl, cat’s eye or cymophane, and alexandrite.
Yellow-green chrysoberyl was referred to as “chrysolite” during the Victorian and Edwardian eras. Which caused confusion since that name has also been used for the mineral peridot as a gemstone. That name is no longer used in the gemological nomenclature.
THe stone forms as a result of pegmatitic processes. Melting in the Earth’s crust produces relatively low-density molten magma which can rise upwards towards the surface. As the main magma body cools, water originally present in low concentrations became more concentrated in the molten rock.
The remnant magma thus becomes richer in water. And also in rare elements that similarly do not fit in the crystal structures of major rock-forming minerals. The water extends the temperature range downwards before the magma becomes completely solid. Allowing concentration of rare elements to proceed so far that they produce their own distinctive minerals.
Igneous in appearance
The resulting rock is igneous in appearance but formed at a low temperature from a water-rich melt, with large crystals of the common minerals such as quartz and feldspar, but also with elevated concentrations of rare elements such as beryllium, lithium, or niobium, often forming their own minerals.
It is pegmatite. The high water content of the magma made it possible for the crystals to grow quickly, so pegmatite crystals are often quite large, which increases the likelihood of gem specimens forming.
In mica schists
Chrysoberyl can also grow in the country rocks near to pegmatites, when Be- and Al-rich fluids from the pegmatite react with surrounding minerals. Hence, we can found it in mica schists and in contact with metamorphic deposits of dolomitic marble.
Because it is a hard, dense mineral that is resistant to chemical alteration, it can be weathered out of rocks and deposited in river sands and gravels in alluvial deposits with other gem minerals such as diamond, corundum, topaz, spinel, garnet, and tourmaline. When found in such placers, it will have rounded edges instead of sharp, wedge-shape forms.
Chrysoberyl crystal rich in beryllium
If the pegmatite fluid is rich in beryllium, crystals of beryl or chrysoberyl could form. Beryl has a high ratio of beryllium to aluminium, while the opposite is true for chrysoberyl. Both are stable with the common mineral quartz.
For alexandrite to form, some chromium would also have had to be present. However, beryllium and chromium do not tend to occur in the same types of rock. Chromium is commonest in mafic and ultramafic rocks in which beryllium is extremely rare.
Beryllium becomes concentrated in felsic pegmatites in which chromium is almost absent. Therefore, the only situation where an alexandrite can grow is when Be-rich pegmatitic fluids react with Cr-rich country rock. This unusual requirement explains the rarity of this chrysoberyl variety.
Chrysoberyl meaning and healing properties
The stone transforms negative thoughts into positive energy. It increases self confidence and strengthens self worth.Chrysoberyl aligns the solar plexus and crown chakras. It opens the crown chakra and increases both spiritual and personal power. The gem is associated with wealth and is excellent for creativity.