Sapphires, much like other valuable gemstones, form deep within the Earth’s crust. Until recently, scientists have struggled to fully understand the specific processes that create these dazzling blue crystals.
A recent investigation by Heidelberg University researchers has explore the formation of sapphires in volcanic areas, providing fresh insights into their origins.
Sapphires primarily consist of aluminum oxide, with various trace elements including iron, titanium, lead, cobalt, chromium, magnesium, boron, silicon, and vanadium. Sapphires owe their stunning blue color to trace elements, especially titanium and iron.
They engage with the crystal lattice and capture light wavelengths in the red and yellow regions of the spectrum.
When these wavelengths absorb, they reflect light that appears predominantly blue, creating a vibrant azure hue.
Ancient volcanic rock, naturally rich in sodium and potassium but low in silicon dioxide, provides the source for the blend of elements.
Researchers examined 223 sapphires discovered in the Eifel mountain range of western Germany. This volcanic region, known for its persistent magma activity, has been experiencing magma penetration from the Earth’s mantle for nearly 700,000 years.
Experts were unclear about why sapphires frequently appear in certain regions, but researchers have now determine that volcanic activity is the key factor.
Geologists believe that high temperatures subject clay sediments in the Earth’s crust to form sapphires. As magma rises and pressure increases, the crystals push toward the Earth’s surface.
Schmidt concludes that both magmatic and metamorphic processes influence sapphire formation in the Eifel region. Temperature variations alter the original rock composition.
“Sapphire, much like gold, is highly resistant to weathering compared to many other minerals. Sebastian Schmidt, a graduate student at Heidelberg University, explained that over extended periods, the rock erodes the sapphire grains, and the rivers eventually transport them.
“Because these particles have high density, you can easily separate them from lighter sediment using a gold pan.”
The analysis of oxygen isotopes and trace elements determined that the sapphires from the Eifel formed concurrently with volcanic activity.
The sapphires acquired their unique isotopic signature from mantle melts. These gemstones interact with heat from partially molten rock that originates three to four miles below the Earth’s crust.
Sapphires also formed when they interacted with underground rock surfaces, initiating the creation of these precious gemstones.
Schmidt concluded that magmatic and metamorphic processes influenced sapphire formation in the Eifel region. Temperature variations altered the original rock composition.
The details of the findings were publish in the journal Contributions to Mineralogy and Petrology.
