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Chrysoprase Chalcedony: Marlborough District,
Queensland, Australia

By Richard Osmond and David Baker

Figure 1. A view from the Candala Chrysoprase Mine of the surrounding area near Marlborough, Queensland, Australia. It is located 87 KM northwest of Rockhampton, Queensland, Australia.

Figure 2. An open cut through a portion Candala Chrysoprase Party Ltd., property lease reveals Chrysoprase veins present on the vertical surfaces. An example of the original property condition is shown just beyond this open trench.

Abstract
Chrysoprase is a form of green cryptocrystalline quartz referred to as chalcedony or chalcedonic quartz. Chrysoprase chalcedony is highly prized in the Asian market and among gemologists worldwide. The Candala chrysoprase mine, also known as the Marlborough Mine is located near Marlborough, Queensland, Australia and is 87 KM northwest of Rockhampton. (figure 1) By the earliest accounts, Marlborough chrysoprase production began in the 1960’s. Removal of the ore bodies from properties adjoining the Candala Mine has resulted in near depletion. In contrast, the Candala mine is virtually “untouched” and provides us the opportunity to visit a site perhaps as close to the original condition of the locale as exists today (figure 2).

Introduction
Chrysoprase is the most valuable stone in the chalcedony group and has been mined since the 14th century in Frankenstein, Upper Silesia (Poland) but this source has been depleted. Since the 1960’s, the finest qualities of chrysoprase have come from Queensland, Australia (Krosh, 1990). The source of other deposits include Brazil, India, Malagasy Republic, South Africa, Russia (Urals), and in the United States (Arizona, California, and Oregon) (Schumann, 1977, p. 128)

Historically, chrysoprase has been associated with bringing good fortune to those who wore it. For example, Volmar is credited with saying, “If a thief sentenced to be hanged or beheaded should place this stone in his mouth, he would immediately escape from his executioners. (Kunz, 1913, p.22) Albertus Magnus stated that Alexander the Great wore a “prase” into battle. With his Indian campaign behind him, it is said that Alexander, wishing to bath in the Euphrates, laid aside his girdle, and a serpent bit off the stone and dropped it into the river (Kunz, 1913, p.69).

Figure 3. This rough chrysoprase is representative of the intensity of color and exceptional quality from this locality.

Geology, Climate, and Location
Chrysoprase from the Marlborough District was found in veins from two to eight inches thick, and the nickel content unusually high (2.35%) and in consequence the color is deeper than most samples from other localities. (Webster, 1983, p. 220) The bright yellow to green color of chrysoprase mined from the Marlborough area is imparted by the presence of minute inclusions of a nickel mineral, probably the Ni-bearing talc mineral, willemseite (Vasconcelos, et al. 2002).

It is believed that a unique geologic formation and combination of superior quality base materials composed of nickel and chalcedony, along with an iron silicrete cap formed above the deposit has protected the deposit from erosion and has allowed for a low percolation rate of waters through the deposit. The hydrology needed for the formation of the chrysoprase deposits in this area was driven from the bottom up and the resulting land formation protected the deposit. The soil constituents have also imparted a superior deep color, with exceptional translucency, and a much lower incidence of fading color that is typically seen from other chrysoprase sources (figure 3).

Typical winter weather in this area of Australia is dry, with temperatures moderate to warm. Summer is described locally as dry and hot, with temperatures in excess of 100 degrees (F)!

The primary commercial mining site for chrysoprase in the Marlborough region is the Gumigil Party Limited lease, and is nearing depletion. The majority of the chrysoprase production from the Gumigil Party Limited lease is shipped to the People’s Republic of China for domestic consumption and is commonly used as a jade substitute. Candala chrysoprase mining operation leases the adjoining property. While walking the Candala lease, you can readily see the outcroppings with bands of chrysoprase chalcedony (figure 4).

Figure 4. Veins of chrysoprase are readily seen on the host rock outcroppings as you walk the Candala lease.

The mine locations in Marlborough, Queensland, Australia are accessible only by 4-wheel drive vehicles and are reached traveling approximately two hours from Rockhampton, Queensland, Australia. Air travel is the suggested mode of transportation from Sydney to Rockhampton.

History
Dick and Jack Moesinger first discovered the Marlborough chrysoprase deposits in the early 1900’s. After sporadic early mining, some hand mining occurred during the 1950’s, with the first mechanized mining taking place during that time. In the early sixties, claims were consolidated with two Marlborough claims
remaining, a large lease owned by Bill Stacey, Sr. and a smaller one, which was later to become the Candala chrysoprase lease, owned by Bert Kayes.

Bill Stacey sold his large claim, which was the Gumigil Chrysoprase Mine to a Chinese mining concern, Po Yuen, which then embarked on a major chrysoprase mining operation that remains open to this day.

Bert Kayes also sold his smaller lease and this property subsequently changed hands several times. ventually Resource Mining Corporation (RMC) leased this property for mining nickel, cobalt, and chrysoprase. RMC conducted an extensive drilling program covering 20% of the lease holdings and discovered ore bodies of ~350 tons of chrysoprase, with much less nickel and cobalt discovered. RMC decided to concentrate on their considerable, more lucrative, ore leases in Western Australia. (Stacey, Pers. Comm., 2007)

Author, Richard Osmond, first heard of the RMC chrysoprase mine in Tucson, February 2005. He visited Marlborough, an Australian cattle farming community and the location of the mine, for the first time in May 2005. Based on the observations of Richard and Mary Lou Osmond and following a feasibility study, they had conversations with local mining personnel associated with the nickel deposits in the surrounding the area. The principals secured an option from RMC, raised capital, and Candala Chrysoprase was formed. Candala Chrysoprase secured the mining lease interests in December 2005.

In Tucson, February 2006, the authors discussed the Candala Mine and the Marlborough District. It was clear that the significance of the site and the material found here has relatively minor exposure in jewelry or gemological publications.

Figure 5. Work performed by hand includes material being screened and washed in preparation for sorting.

Mining Methods
While other mines use aggressive mining techniques to yield higher volume, to date, mining at Candala is performed mostly by hand and with limited fully mechanized machinery. This material is handpicked, washed, and then sorted (figure 5). This allows the owners to recover the largest examples of chrysoprase material that can be finished into exceptional gemstones and carvings (figure 6). Very high-grade round beads are produced as a result of this slow, methodical approach and technique of recovery. Care and attention must be maintained while walking the hillside mine (figure 7). At times, maintaining secure footing is challenging in the loose mining material, with consideration of the ever-present snakes and lizards within this locale. (Authors, per. Comm. 2007)

Figure 6. Rare druzy Chrysoprase is also found by careful “light mining” techniques resulting in the discovery of fine specimens of smaller size often missed by a more mechanized mining operation.

Figure 7. The hillside area of the Candala lease and the older tailings dump are shown. Due to the loose fill conditions, care and consideration must be given to maintaining footing.

Figure 8. Examination of finished cabochon cut chrysoprase confirms the reason for interest by collectors in search of an alternative to the finest “Imperial” Jade.

Material & Gemological Properties
The color of the highest gem quality chrysoprase, as observed by the authors, is a translucent green hue, of medium to strong intensity, and a medium or darker tone. It is this color that duplicates the appearance of the finest jadeite jade that has intrigued and fascinated the Chinese for centuries (figure 8).

While this property does yield a variety of qualities of chrysoprase, it is primarily very high quality, translucent, nearly transparent gems of medium green or darker, and free from any internal fractures. Slabs have been seen at the Candala location weighing several kilos and there are boulders present at the Candala mine location in lower qualities up to approximately 18 tons (figure 9).

Current annual production at Candala mine is 15 metric tons per year. The traditional “Grade A” Marlborough chrysoprase, recognized as finer than chrysoprase produced at any other mine site in the world, consists of 4.5%. The absolute gem quality chrysoprase is a very small percentage (.05% = approximately 50 kilograms) of total production. (R. Osmond, pers. Comm., 2007)

Figure 9. An example of boulders found on the southern area of the Candala lease. Many exceed 18 tons.

Most chrysoprase is exported to China, Bali, Indonesia, and Brazil for fabrication. Fabricated and un-fabricated chrysoprase is sold in the US market. To Candala Mines, the largest known fashioned item of absolute gem quality Candala chrysoprase is a lion’s head cane handle.

Conclusion
The Australia chrysoprase mine locations in Marlborough District, Queensland, are synonymous with the finest chalcedony ever produced. The gemological community is very familiar with Chrysoprase, yet very little has been reported about this important gem-producing location. The Australian Outback is certainly an appropriate backdrop for the intriguing history and geology of the Marlborough mines. The excitement of gem discovery, connections made, and the sharing of gem knowledge is alive and well in the United States. It continues every February in an unlikely place in the middle of the desert - Tucson, Arizona.

Chrysoprase has passed the test of time and it possesses the requirements to be considered a gemstone: beauty, rarity, and durability. The exceptional quality chrysoprase rivals the finest green jade. With production waning at the Gumigil Party Limited lease, the production at Candala chrysoprase is on the increase. Interest and appreciation for this gem material continues to grow and no new mine sites have been discovered.

REFERENCES
Krosh, N. J. (1990) Queensland chrysoprase. Australian Gemmologist 17, 303-306.
Kunz, G.F. (1913) Curious Lore of Precious Stones, p.22; p. 69
Schumann, Walter (1977) Gemstones of the World, p. 128
Vasconcelos P., Cohen B., Calos N. (2002) Colour in quartz: from atomic substitutions to nano inclusions. Australian Gemmologist, Vol. 21, p. 278.
Webster, Robert (1983) Gems: Their Sources, Descriptions, and Identification, Fourth Edition, p. 220

ABOUT THE AUTHORS
Richard Osmond, an Australian native, has spent 20 years in the gemstone industry. Mr. Osmond is the Chief Executive Officer for Candala Chrysoprase, with International Headquarters in Drummoyne, NSW, Australia. In addition, he is responsible for worldwide marketing of Candala Chrysoprase. David Baker is a Graduate Gemologist-Gemological Institute of America, Personal Property Appraiser-Specialty Jewelry & Gemstones, in Houston, Texas. Mr. Baker is an Accredited Member-International Society of Appraisers, Senior Member-National Association of Jewelry Appraisers. He is an internationally recognized gemologist, invited speaker & published author in the field of Gemology.

ACKNOWLEDGEMENTS
Mr. William Stacey, Senior Site Executive & Site Manager, Marlborough Nickel Pty Ltd. provided invaluable assistance for his expertise and knowledge of the local Marlborough area. Mr. Chirachai Tang, Oriental Trading Group Co., Ltd. Bangkok, Thailand, provided cutting services for chrysoprase samples. The authors are grateful to Fredika M. Robertson, Ph.D., and Mary Lou Osmond for their input, technical expertise, support, love, and continued understanding.

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