Gobi Agate History

1. GOBI DESERT FORMATION

The Gobi Desert covers an area of more than 4.0 million km2, occupying territories in Mongolia and northern China, lying along the depression between the Altai and Khangai Mountains. The terrain is wonderfully varied, with formations of undulating dunes, deep ravines, panoramic plains, steep cliffs, and narrow canyons. The climate of the contained areas is generally dry and the vegetation cover is altogether sparse, resulting in substantial dust emission which affects the regional and even global climates.

Various processes over more than four billion years resulted in the establishment of the modern Gobi Desert landscape in the late Pliocene. Most estimates are that the modern Gobi Desert landscape was formed 2.6 million years ago and was the result of the stepwise evolution of Asian topography and climate during the Cenozoic, dominated by tectonic deformation and uplift, and the evolution of Asian monsoon climate with westerly circulation, forced by global temperature change (Lu et al. 2019). The world’s highest mountain chain, the Tibetan Plateau, blocks clouds from the Indian Ocean, preventing rain from reaching the Gobi.

Because of the extremely arid climate and large diurnal temperature range, the Gobi Desert regions experience strong physical weathering, which generates large quantities of silt particles (Amit et al., 2014; Cui et al., 2015, Cui et al., 2019; Sweeny et al., 2016). Through forces of dislocation of the Altai Mountains and volcanic activity, rock types in the region are rich and varied. The tectonic structures bear commercially-exploitable deposits of iron, as well as rare metals such as mercury, gold, manganese, tungsten, and marble. Massive coal, copper, and gold deposits are concentrated in the eastern part of Umnugobi Province, with oil and uranium in the southwestern region.

Please find citations and references on our “Citations and References” page. 

2. AGATE FORMATION

Agate specimens are formed when silica-rich groundwater fills cavities in rocks, called vesicles, and crystallizes into layers over thousands of years. The process has been simplified below: 

1. First, a cavity forms. Volcanic rocks, like basalt, are filled with holes that form when gases trapped in the liquid lava bubble out. 

2. Silica-rich groundwater penetrates the vesicles. Groundwater rich in silica percolates through the rock and into the cavities. 

3. Crystallization occurs. Minerals in the water crystallize out, forming layers on the vesicle walls. The first layer is called the priming layer. Variations in solution and deposition conditions cause the layers to vary, resulting in bands of chalcedony and crypto-/crystalline quartz. When the silica-rich liquid doesn't fill the cavity completely, hollow agates can form. 

Agates are most commonly found in volcanic rocks because igneous rocks are better at holding groundwater over long periods of time. The youngest volcanic rocks, basalt, are the best candidates for agate formation, but agates have also been found in materials such as fossilized dinosaur bone. Agates are less likely to form in sedimentary or metamorphic rocks because these rocks are more porous and allow groundwater to move through them. 

Studying agates with transmission electron microscopy and by x-ray diffraction, approximately ninety percent of an agate is made up of quartz crystal structures. But there is another mineral present that has the same chemical composition, SiO2, and a different structure: moganite. Similar to carbon, which can crystallize into both diamond and graphite, nearly ten percent of an agate will be this other structure, moganite.” (Heaney, 2001) 

When agates are observed with a simple light microscope, fibrous crystal structures are evident. They nucleate on the wall and radiate inward like spokes on a bicycle wheel. Usually this first layer, the priming layer, is chalcedony, a mixture of quartz and moganite. Then there are coarse-grained quartz layers—pure quartz, no moganite.

The longstanding question, then: "Why do you see different layer types?”

The layers are both silicon dioxide, but what is changing is the crystal structure.

Those repeating changes in crystal structure (size, type, and direction) scientists believe, cause the characteristic banding pattern of agates, with colors coming from trace elements like iron or manganese.

As agate minerals have the tendency to form on or within existing rocks, difficulties are created in accurately determining their time of formation (5). Their host rocks have been dated to have formed as early as the Archean. Slowly, over time, the encasing rock—or bone—weathers away, leaving just a roundish, rough lump.  And invariably, most agates last longer than their surroundings. 

3. AGATE FORMATION IN THE GOBI DESERT

The structures of Gobi agates would have formed similarly to other types of agates around the world. Volcanic activity in the Altai Mountain Region would have left large basalt depositions for silica-rich groundwater to infiltrate. Additionally, the rare metal compositions within the geographic area of Gobi agate distribution lend to the intense and varied colors found in regional specimens. 

Once included sections of rock are dislodged, or exposed to the elements, the mineral matrix surrounding Gobi Agate stones is worn away by water, wind, and sand. Due to the number of geological processes at work in the region, many Gobi Desert Agates have been weathering, loose, since the time before the desert was a desert. 

Environmental laws preserve the land and processes that create these unique gemstones. The Mongolian government has established protected areas to conserve the Gobi's biodiversity, including Gobi Gurvan Saikhan National Park and the Great Gobi Strictly Protected Area. The Great Gobi SPA is divided into two ecologically distinct parts, Southern Altai and the Dzungarian Gobi, separated by some 300 kilometers from each other. The two parts together span an area of 5.5 million hectares, making it one of the largest terrestrial protected areas in the world; it is free of mining and industrial activities, and has few inhabitants. Any adjacent mining and extractive organizations must have an environmental protection plan and carry out technical and biological restoration.

Gobi Desert Agates are traditionally collected by nomadic groups or individuals and sold to brokers in population centers. Certain Mongolian cities are known for their public bead markets, but these are secondary markets. The primary market, which trades in the highest-quality and most prized specimens, exists between brokers and collectors, mostly in Mainland China, and all but ensures the most desirable gemstones do not reach the general public. 

Greenly & Co. sources entirely off-market, directly from brokers and collectors in the Inner Mongolian Autonomous Region.

4. CULTURAL SIGNIFCANCE, PT. 1

Gobi Desert Agates are regarded as personal talismans, powerful embodiments of various virtues. The culture surrounding these stones focuses on type—certain colors, shapes, and constructions are more valuable than others. 

In particular, Agate stones have a deep, entwined history with the two-thousand year-old tradition of “Viewing Stones.” The most common viewing stones—and easiest to understand—are ones that resemble aspects of natural scenes such as mountains or mountain ranges, plateaus, arches, waterfalls, or other landscapes. Stones may be abstract in form; others may suggest a structure such as a boat or a hut, or they may suggest a figure, real or mythical. Seated “Buddah” aggregates are particularly enticing. Gemstone-quality specimens containing shapes resembling persons or animals are among the most expensive viewing stones in China today. 

Besides as viewing stones, Gobi Agate beads are highly desirable, and highly collectable if they have been curated as part of a set for size, shape, and color. For beads, natural roundness is prized above all else, as it is exceptionally rare to find in nature. Full sets of round beads, as in a necklace, can take as many as ten years to collect in a matching or graduating set, and command the highest prices on the market. 

Recently, a run on “Strawberry Agates” increased the visibility and price of the type—a type with specific color and composition, as shown. We discuss in greater detail the stories and culture around individual bead types in: “TYPES OF GOBI AGATES.”