At first glance, a Mexican Jelly Opal might not seem like much ā just a soft, golden-orange gem with a glassy finish. But then something magical happens: you hold it up to the light, and it explodes in colour. Welcome to the dazzling world of contra luz opals.
What does ācontra luzā mean?
āContra luzā is Spanish for āagainst the light,ā and it perfectly describes how this gem works. Unlike other opals that flash their colours in direct lighting, contra luz opals only reveal their fire when backlit ā think of sunlight shining through a stained-glass window.
This spectacular light show is caused by the opalās internal structure. As white light enters the stone, it hits tiny silica spheres and scatters. That scattering creates a fiery burst of colour that appears to glow from within.
The science behind the sparkle
Opals form when silicon dioxide ā basically, the building blocks of glass ā mixes with water underground. Over time, this silica-rich water seeps into cracks, voids, or spaces left by decayed fossils. As the water slowly evaporates, it leaves behind a silica deposit.
This process repeats over thousands or even millions of years, forming the stunning gem we know as opal. The size, shape, and arrangement of those silica spheres determine how much colour the opal shows ā and in the case of contra luz opals, it creates a fire thatās only visible in transmitted light.
Why gem lovers are obsessed with it
Contra luz opals are all about the element of surprise. They keep their colour hidden until the moment is just right ā and when it is, they show off with an intensity that rivals any fire opal or play-of-colour specimen.
Whether youāre a gem collector, a jewelry designer, or just love discovering natureās optical tricks, contra luz opals are the kind of stone that stops you in your tracks.