Gem Profile- Rutilated Quartz

by Judy Ellis

Rutilated Quartz

This week I thought we'd try something a bit different. We're going to take a look at two different types of minerals with different chemical compositions, hardness and even form at different temperatures under different types of environments; yet they are often found together. When I say together, I mean literally; one growing within the other. So how does this happen? Science hasn't quite figured that one out yet, but they're working on it.

What is Rutile?

The first mineral we are looking at is Rutile. Last week, we learned that rutile creates chatoyancy and is responsible for the stars, or asterism, in gemstones.

Rutile is composed of titanium dioxide. This is a main component of refractory ceramics, titanium metal, and the bright white pigment used in plastics.

Interestingly, it is also used in sunscreen because of its ability to absorb ultraviolet (UV) light. Rutile has a titanium base, but it can create different colors and effects within a stone when associated with other minerals.

We will discuss golden rutile later in this post.

Synthetic rutile has existed since the late 1940s and was once used as a diamond substitute called "Titania." At only 6 on the Mohs scale, it is not durable and is rarely used in jewelry now.

Rutile, whether natural or synthetic, is a 6 on the Mohs scale. It is generally found in volcanic regions and associated with quartz in various areas worldwide.

Though rutile forms at lower temperatures than quartz, it is often found inside quartz crystal. When rutile grows within quartz, the material is named rutilated quartz.

Adrien De Ruyck created this lovely ring with a rectangular clear quartz with reddish brown and black rutiles.

About Quartz:

Quartz is one of the most common minerals on Earth, found on every continent and making up 12% of the Earth's crust. It is quite common.

Quartz is created under high temperatures and pressure. Varying inclusions give us different types, ranging from clear to rose and smoky.

One of the most beautiful types of included quartz is rutilated quartz. It can be found in Australia, Brazil, Kazakhstan, Madagascar, Norway, Pakistan, and the United States.

Golden rutilated quartz was first discovered in Brazil in the Serra da Mangabeira mountain range in the 1940s. Miners were initially collecting clear quartz for optical uses.

The included rutilated quartz was simply discarded because it had little value in optical applications. Eventually, some of the material made its way to Bahia, Salvador, where gem dealers recognized its value.

A beautiful piece of golden rutilated quartz.

The rutilated quartz from this region has beautiful golden threads throughout the stone.

This golden rutile is associated with hematite and grows in impressive thick strands within the quartz.

Because golden rutile is composed of titanium dioxide, it has high concentrations of hematite.

The rutile responsible for asterism, conversely, is mostly asbestos.

This type of rutile rarely forms stars. Instead, it creates beautiful, long, thin needles of color due to its orientation along the axis during development.

Since quartz has a hardness of 7 and rutile is a 6, it can be difficult to cut and polish a rutilated stone.

This difference in hardness can easily lead to pits and cracks in the quartz.

Golden Rutilated Quartz Cab. Photo provided courtesy of Adrien De Ruyck

Tying it all together!

How does rutile form within quartz? Quartz forms at extremely high temperatures and pressures, usually associated with volcanic activity.

When lava degases, it creates vugs (bubbles) and pegmatites, which form large crystals during the final cooling stage.

One theory suggests that quartz permeates a vug, and then the rutile precipitates and grows within the stone as it cools.

The other theory is that as the quartz pegmatite cools, it develops microscopic cracks that allow the rutile to grow inside.

Either way, the rutile strands develop within the quartz. This process gives us a beautiful color show of long, thin needles inside a clear stone.

Because of its appearance, rutilated quartz is also known by the names Bahia Gold, Venus Hairstone, and Cupid's Darts.

Lemon Quartz wrapped in gold filled and rose gold filled wire with Swarovski crystals and pearls. Created and photographed by Sherry Dusza

At the time of this article we are carrying a variety of Designer Rutilated Cabochons in both Black Agate and Lapis. Please click here to see what we still have available!

Resources & Recommended Reading

On Mindat.com - Gemstone discussions about Rutilated Quartz
Wikipedia

A special thanks to Brian Charles Cook:

www.aromajewels.com
www.naturesgeometry.com

Gem Profile- Rutilated Quartz

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