ISG The Story of Petrol Quartz

A fantastic look at a very unique form of quartz with astounding inclusions.

Few gemstones provide as much fun as quartz. The amazing variety of inclusions found in quartz crystals makes this one of the most popular for collectors from all segments of the industry.

We recently had the opportunity to add to our collection of petroleum-included double-terminated quartz crystals from Pakistan. These unique specimens offer formations as different as snowflakes.

As you can see in the image at left, the petroleum occurs in negative crystals and pockets inside the crystal, attesting to the fact that this petroleum was protogenetic to the formation of the crystal, meaning that the petrol was already in the hydrothermal (hot water) mix that hosted the formation of the quartz crystal. But the question is, how did crude oil (petroleum) get inside a quartz crystal?

Let us go back millions of years to the ancient oceans filled with phytoplankton. These microscopic plants performed the process of turning energy from the sun into food and more phytoplankton. Over millions and millions of years, these phytoplankton died and drifted to the bottom of the sea floor, where they were covered by millions of years of ocean sediments. Eventually, the pressure and heat from the sediments squeezed the remnants of these tiny plants into a liquid known as crude oil. This crude oil is captured between layers of rocks deep in the earth. This is where the magic happened.

Fissures developed in the rock that hosted the petroleum. These fissures allowed high-pressure, silicon-rich hot water to rush into the rock formation containing the petrol. On the left, you can see an example from one of our ISG field trips to the pegmatite dikes of Mason County, Texas. The white lines running through the billion-year-old metamorphic rock demonstrate a time when this area was deep underground, and this hot water smashed into the fissures. As the water slowly cooled, the remaining silicon formed the white quartzite rock you see running through the black host rock.

If the hydrothermal intrusion is allowed to cool slowly enough, crystals of various gemstones can form within the void created by the fissure. Below you see part of the intrusion from our field trip showing pink feldspar crystals with white quartzite. If allowed to cool very slowly under the right conditions, then clear quartz crystals will form.

If the host rock happens to contain the petroleum liquid from our ancient phytoplankton when the quartz crystals form, the petroleum is engulfed into the crystals as they grow, forming petrol inclusions inside them, as seen on the left.

Just like sitting out on a partly cloudy day looking for shapes in the clouds, I have a great time looking for shapes in our petrol inclusions quartz crystals. At left is a new image that I am terming the “parrot fish” for the variety of fish in the Caribbean that eat coral. The eyes and beak sort of form the……OK, you have to use your imagination. If we have to explain it, you probably will not see it anyway. But looking in the microscope at petrol inclusions in quartz, it is always fun to turn the stone in various directions to see if we can pick out a shape here and there.

Below is the now famous “petrol frog” photographed a few years ago in our original specimen. This image has caused great chaos for many who don’t know it actually contains petrol inclusions.

One of the most fun features of this petrol in quartz is that the petrol is highly fluorescent, as you see in the image at left.

Below are two slides of the same petrol quartz in ambient light and ultraviolet light, demonstrating this remarkable property of petrol quartz.

The Story of Petrol Quartz is not just a simple inclusion study; it is the story of millions of years of history that went into creating this amazing gemstone. After all, the petroleum in the ground was not all just phytoplankton. Some was likely made from the bodies of dinosaurs and ancient sea creatures. In fact, maybe….just maybe…your petrol quartz crystal contains the remnants of an ancient Tyrannosaurus Rex, a Brachiosaurus, or maybe even a Megalodon Shark!

This gemology stuff, it ain’t rocket science.

But it sure has some fun history in it.