La Belle De Jour: A Giant Emerald Matrix

La Belle De Jour is exquisitely encrusted with rough emerald formations that travel inwards as well as inclusions of materials such as molybdenite, granitoid gneiss, and quartz on schist. This matrix also contains traces of metals, such as gold, chromium, tungsten, aluminum, zinc, and nickel.

Where Was La Belle De Jour Found?

After more than 600 million years underground, this specimen was unearthed on a sunny day in Serra da Carnaíba, in the province of Bahia, Brazil. Extracted from a depth of over 500 ft (~150 m), this beautiful, large black schist contained nine large clusters of emerald crystals as well as green beryls.

The formation of this specimen began during the Precambrian period of Earth's prehistory, which spans from 4.6 billion years ago to 541 million years ago. As G. Giuliani, L.J.H.D. Silva, and P. Couto note:

Precambrian emerald deposits of Brazil are found in a typical geologic setting with Archean basement and supracrustal, ultramafic, granitoid and rocks. Volcano-sedimentary series occur as imbricated structures or as bodies affected by complex folding and deformation. Emerald mineralization belongs to the classic biotite-schist deposit, which formed by the reaction of pegmatitic veins within ultrabasic rocks.

Bahia has yielded two other rare emerald formations: the (in)famous "Bahia Emerald," valued as high as $925 million USD (and as low as a hundred dollars) and, more recently, an unnamed matrix valued at R$500 million Brazilian Reais (about $151 million USD).

Our specimen was baptized with the name of La Belle De Jour. Everyone who laid their eyes on it immediately admired it. On March 27, 2018, the piece was imported into the United States. Florida became its new temporary home.

The Artistic Process

After I viewed the unearthed emerald matrix, I was inspired to create a base that would showcase its majestic color, form, and size: three arms rising up from the Earth, offering La Belle De Jour to the world.

The copper base weighs over 80 pounds and took over 500 hours to complete. It took a combination of modeling, hand carving, and casting to go from imagination to stone model to copper cast. This base is a masterpiece in itself, showcasing the emerald matrix in all its splendor.

Definitions

The following definitions will help you understand the detailed description of the La Belle De Jour.

Anhedral

A mineral crystal that has no external faces.

Emerald

The green variety of the mineral species beryl (Be₃Al₂Si₆O₁₈) with trace amounts of chromium (Cr) and/or vanadium (Va) as the cause of color. 

Euhedral

A mineral crystal with well-formed faces. 

Green Beryl

Another green variety of beryl with trace amounts of iron (Fe) as the cause of color. This variety shows a green to slightly yellowish green color and lacks the bright, blueish green tone of emerald. Green beryls also occur more frequently than emeralds.

Matrix

In geology, the material that embeds something, such as the natural rock that holds crystals, fossils, pebbles, mineral veins, and the like. 

Molybdenite

This sulfide mineral (MoS₂) is an ore for the metal molybdenum. It looks like graphite and has a greasy feel and a lead gray color. Slices of this material are actually flexible.

Prismatic

Mineral crystals that display a uniform cross section and well-developed, prism-like faces.

Schist

To the naked eye, this material looks like crystalline rock. It has high schistosity, a tendency to cleave along parallel planes into layers. Most schists consist principally of platy minerals, such as muscovite, chlorite, talc, sericite, biotite, and graphite. La Belle De Jour is described as a black schist due to its high black mineral content, most probably biotite (iron-rich brown-black mica) and other dark colored minerals.

Terminations

In mineralogy, flat surfaces or faces at the end of a crystal. If flat faces appear on just one of a crystal, the crystal is said to be singly terminated. If flat faces appear on both ends, the crystal is said to be doubly terminated. Crystals with no flat surfaces on either end are said to be non-terminated.

An Overview of La Belle De Jour

Please note that all dimensions are approximate.

La Belle De Jour is a large black matrix containing prismatic, non-terminated emerald crystals, massive green beryl blocks, and anhedral molybdenite crystals. Overall, it measures approximately 20 x 14.5 x 15 inches (~50.8 x 36.8 x 38.1 cm). Its widest circumference measures 54 inches (~137 cm). It weighs a solid 256 pounds (~116.2 kg). This specimen shows no evidence of polishing, repair, or other type of enhancement.

The emerald crystals range in length from 2 to 6.5 inches (~5 to 16.5 cm) and width from 1 to 2.5 inches (~2.5 to 6.3 cm). These crystals show a medium to light, slightly blueish green color as well as color zoning at places. Their transparency ranges from translucent to opaque.

The massive, anhedral green beryl blocks show a light, slightly yellowish green color. These green beryls are entirely opaque and intergrown with smaller emerald formations. 

The sides and the back of La Belle De Jour don't contain any large emerald crystals. However, some emerald growth is visible within green beryl at the back and right side of the specimen. In these areas, large green beryl forms the majority of the structure. The left side of the specimen consists mainly of black matrix.

A Detailed View of La Belle De Jour

La Belle De Jour contains nine large emerald crystal clusters. Some of these clusters consist of two to three crystals grown together within black schist matrix. These are found mainly at the front of the specimen. Only one occurs on the back of the rock, at the top side of the specimen. However, it's still visible from the front (Cluster 5). I've marked and numbered the clusters in this photo.

Cluster 1

A few intergrown prismatic emerald crystals with green beryl base and black matrix inclusions. None display termination. The crystals have a glassy or vitreous luster, and some faces show growth lines. Approximate measurements are 4 x 2.5 inches (~10.2 x 6.4 cm).

Cluster 2

Prismatic emerald crystals intergrown within a larger anhedral green beryl. No termination. The cluster is next to a few anhedral molybdenite inclusions. The largest emerald crystal measures approximately 2.75 x 1 inches (~7 x 2.5 cm).

Cluster 3

A cluster of prismatic emerald crystals, measuring approximately 6.5 x 1.5 inches (~16.5 x 3.8 cm), lies next to a smaller anhedral emerald, around 1 inch (~2.5 cm) in diameter. This piece is entirely opaque with obvious color zoning at the top. The right side of the crystal cluster displays a more distinct prismatic face compared to the rest.

Cluster 4

Three emerald crystals grown together with green beryl. The cluster measures approximately 4 x 2 inches (~10.1 x 5 cm).

Cluster 5

Three opaque, intergrown emerald crystals displaying color zoning, measuring approximately 1 x 2.75 inches (~2.5 x 7 cm).

Cluster 6

Opaque, intergrown emerald crystals with green beryl at the base, where it's attached to the matrix. The cluster measures around 5 x 2 inches (~12.7 x 5 cm), and very small, 1-2 mm long needle-like black crystals cover its top. The cluster displays a break and natural healing structure in the middle.

Cluster 7

This larger, opaque crystal displays the least luster of all the clusters. It also shows a green color with a lower level of saturation than the other clusters. It measures around 3.75 x 1.5 inches (~9.5 x 3.8 cm).

Cluster 8

This smaller, single emerald crystal, attached to a green beryl base, displays the best luster and color of all the crystals. Linear growth lines on the crystal surfaces, parallel to the C-axis, are visible. It measures 1 x 0.75 inches (~2.5 x 1.9 cm).

Cluster 9

Two opaque to translucent, parallel-grown crystals display color zoning with some small, black, needle-like inclusions at some surfaces. The top crystal measures 3.5 x 2 inches (~8.9 x 5 cm). The bottom one measures 3.75 x 1.25 inches (~9.5 x 3.2 cm).

Conclusion

Private collectors, museums, and universities will covet such a rare and remarkable piece. No other specimen can equal La Belle De Jour. Perhaps it will take another 600 million years to unearth another one that can come close to it. Who knows?

One thing we do know: whoever acquires this natural beauty will also acquire a piece of time, a piece of wonder, a piece of Earth's history that will surely mesmerize all who look at it.