Chrysoprase Chalcedony: Marlborough District, Queensland, Australia
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. 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.
Chrysoprase Chalcedony is the most valuable stone in the Chalcedony group. Chrysoprase 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. The source of other deposits include Western Australia, South Australia, 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).
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 a colloidal nickel clay compound, possibly garnierite. (Sinkankas, 1964, p. 437)
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.
Located just inside the tropics 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)!
Until recently the primary commercial mining site for Chrysoprase in the Marlborough region was the Gumigil Party Limited lease, and is nearing depletion. All 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 which holds, large, yet to be developed resources of Chrysoprase. While walking the Candala lease, you can readily see the outcroppings with bands of Chrysoprase Chalcedony.
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. Access to the mining areas is gated and controlled by permanent on site security. Air travel is the suggested mode of transportation from Sydney to Rockhampton
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. Eventually 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 lesser amounts of nickel and cobalt discovered. RMC decided to concentrate on their considerable, more lucrative, ore leases in Western Australia.
Author, Richard Osmond, first heard of the RMC Chrysoprase mine , known as Candala Pty Ltd, 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 formed a syndicate with included an American investor, from Chicago, secured an option from RMC, raised capital, and Candala Pty Ltd was purchased. The syndicate secured the mining lease interests in December 2005 and began business under the name of Candala Chrysoprase.
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 never been given the recognition in any jewelry or gemological article.
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. This allows the owners to recover the largest examples of Chrysoprase material that can be finished into exceptional gemstones and carvings. 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. At times, maintaining secure footing is challenging in the loose mining material, with consideration of the ever-present snakes and lizards within this locale.
Material & Gemological Properties
The color of the highest gem quality Chrysoprase Chalcedony, 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.
While this property does yield a variety of qualities of Chrysoprase Chalcedony, it is primarily very high quality, translucent, nearly transparent gems of medium green or darker, and free from any internal fractures that is most sought after. 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.
Most Chrysoprase Chalcedony material is exported to China, Bali, Indonesia, and Brazil for fabrication. Fabricated and un-fabricated Chrysoprase is sold in the US market.
Color Hue: Green, Tone: Light to Dark, Saturation:
Transparency: Semitransparent to Translucent
Specific Gravity: + 2.60
Hardness (Mohs) 6.5 to 7
Luster: Vitreous to Greasy
Fracture-Concoidal, waxy to dull, sometimes granular
Chelsea Filter Reaction-None
Ultra-Violet Fluorescence: None
Often Confused with jadeite, jade substitutes, prase, opal, prehnite, smithsonite, variscite, poor qualities of emerald, bowenite, serpentine, and glass
The Australia Chrysoprase Chalcedony mine locations in Marlborough District, Queensland, are synonymous with the finest chalcedony ever produced. The gemological community is very familiar with Chrysoprase Chalcedony, 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 Chalcedony 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.
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 Sydney, 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.
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. The authors are grateful to Fredika M. Robertson, Ph.D., and Mary Lou Osmond for their input.