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Papua New Guinea is geologically prospective for large, medium and small mineral discoveries. All profitable developments to date have been very large mines but for every large mine there should be many small mines which could be developed under appropriate circumstances.The Papua New Guinea Government should, with appropriate changes to fiscal, legislative and policy regimes, create a favourable exploration envir-onment to encourage a major increase in exploration by small exploration companies and subsequent discoveries and mine development.

Jan 1, 1994

By Dennis S. Kostick

Soda ash is the common name for sodium carbonate (Na2CO3), an alkali compound that is the 11th largest inorganic chemical in terms of production of all domestic inorganic and organic chemicals, excluding petrochemical feedstocks. Despite that most people have never heard of soda ash, it is an important industrial compound used to manufacture glass, chemicals, soaps and detergents, pulp and paper, and many other familiar consumer products. Natural alkalis have been used by mankind for thousands of years; however, their industrial manufacture dates back to only the latter half of the 18th century. Natural deposits of sodium carbonate have been known as early as about 3500 BC, when the Egyptians used natural soda ash in making glass. They also mixed lime and soda ash to make sodium hydroxide (caustic soda) that was combined with silicate minerals found in the Sinai desert. This made a soluble silica, which when added to aluminum-rich silt from the Nile River, produced a silica- aluminate cement mortar with excellent bonding properties for construction. The Romans in the first century AD also used natural soda ash in glass manufacture but expanded its use medically for the treatment of colic pains and skin eruptions, and in the making of bread. Elsewhere, people used the ashes of wood to obtain their source of alkali. People learned over time that different types of wood yielded various ashes with different properties; therefore, various plants were burned specifically for their ashes. Ash from plants grown in salt-bearing soils (such as saltwort) and from kelp and other seaweeds, especially Spanish barilla, were so different from ashes obtained from other vegetation that it became known as soda ash (due to its sodium content) versus pot ash, a potassium-based alkali ash. About 13 t of barilla ashes produced 1 t of sodium carbonate and 14 kg of iodine as a byproduct. The difference between these two ashes was relatively obscure until Duhamel Dumonceau made the distinction clear in 1736. The word soda ash developed from common usage and is perhaps more well known today than its synonym sodium carbonate. One of the primary ores of soda ash is trona, a sodium carbonate-bearing mineral that's name is traced back to Arabic origin. Trona also is known internationally by other names such as urao (Venezuela), kaum (Nigeria), natron (from Greek nitron and Latin natrium), and szekso (Hungary). The beginning of the Industrial Revolution in Western Europe in the late 18th century soon put a strain on the availability of raw materials to meet consumer demands. One of these scarce materials was soda ash. Because of the Seven Years War with England and the Napoleonic wars with other parts of Europe, France could not obtain sufficient quantities of Spanish barilla or other supplies of vegetable alkali to meet the growing demand. Efforts were needed to synthesize soda ash. In 1775, the French Academy of Sciences offered a large prize of 2,400 livres to someone who could find an inexpensive method to make soda ash. In September 1791 at St. Denis, Nicolas Leblanc (1742- 1806), a French chemist, developed such a technique using salt, sulfuric acid, coal, and limestone. The French Revolution interfered with its development, and his patent and factory were confiscated with Leblanc receiving only token compensation. Napoleon returned his factory to him; however, Leblanc was not able to raise enough capital to reopen it, and he committed suicide in 1806. A small, but not particularly successful, Leblanc plant was established in England in 1814. It was not until 1823 when the process first became commercially successful in Liverpool, England. The process was introduced in Germany in 1843 and in Austria in 1851 (Harness and Coons, 1942). Soda ash production by the Leblanc process reached its peak of about 599 500 t in 1880, after which it began to decline as the Solvay process became more popular. The Leblanc process was used to a limited extent in Europe during World War I but had disappeared by World War II. The Solvay process, also known as the ammonia-soda process, was developed by Alfred and Ernest (1 838-1922) Solvay in 1861 based on a concept by Fresnel that had been known since 1811. For the next 50 years, the implementation of the idea evaded industrial chemists because no large-scale and economic means could be found to commercialize the concept. Although Ernest Solvay was unaware of the existance of an ammonia-soda concept, he solved the problems by utilizing carbonating towers. The Solvay process produced soda ash from salt, limestone, and coke, with ammonia as a catalyst. With a capital of 136,000 francs, the first plant was built by the Solvay brothers at Couillet, Belgium, in 1863 with production commencing in 1865. Synthetic soda ash production amounted to 1.5 tpd in 1866, but reached 10 tpd by 1872. They patented their use of carbonating towers in 1872 that had made ammonia-soda manufacturing a successful continuous process. Their second plant was built in 1872 at Dombasle, France. In 1874, the first Solvay plant in England was built at Northwich by Ludwig Mond, the namesake of Brunner Mond and Co. (formerly Imperial Chemical Industries), the company that currently operates the two English Solvay plants. In the United States, William B. Cogswell in February 1879 heard a presentation on the Solvay process and sailed to Europe to meet with the Solvay brothers to seek their support for using their process in New York. At first, the brothers were not interested; however, Mr. Cogswell was persistent and ultimately gained their support. The Solvay Rocess Co. was formed Sep. 2 1, 1881, and construction began immediately on the first Solvay plant at Geddes, near Syracuse, NY. The plant came onstream Jan. 10, 1884, and produced 11 180 t in its first year of operation. In 1910, rotary calciners were installed that increased capacity to 1 000 tpd. By 1930, plant capacity was up to 2 400 tpd. The facility remained in continuous operation for more than 100 years. By 1939. 10 Solvay soda ash plants were in operation in 6 States throughout the nation. The Syracuse plant was officially closed Jan. 6, 1986, with total shutdown completed by Feb. 1986. Ironically, this facility was the first Solvay plant as well as the last. Other than the first Solvay plant beginning in 1884, the majority of US soda ash supplies during the 19th century came from imports. The remainder of the US supply

Jan 1, 1994

The geotechnical and environmental aspects of heap leaching are very closely tied during design, operations and closure. Potential environmental impacts from heap leaching are mostly due to land disturbance and water quality issues, including both groundwater and surface water. Water quality issues are mostly related to containment design, which is primarily a function of proper sizing of the facilities and site specific liner design. Geotechnical analyses is the dominant discipline in providing cost efficient, operationally effective and environmentally sound heap leach facility designs. Much has been published on geotechnical aspects of heap leach design, for example Van Zyl, Hutchison and Kiel (1988) and Van Zyl (1987). This paper will emphasize a few specific aspects related to the geotechnical and environmental consideration for heap leach projects. These aspects are: ò site investigation; ò containment design; ò slope stability; ò heap flow dynamics; and ò closure design. Design of a heap leach project must consider not only the operating life but also closure and post-closure considerations. As a matter of standard practice, designing for closure is an extremely important concept. Not only is it important for environmental aspects, but experience also shows that projects designed for closure will be overall more economical for the total life cycle of the project. Closure considerations are also important during project feasibility evaluations to ensure that total life cycle costs are evaluated.

Jan 1, 1994

By Vic Casaletto

"IntroductionThe Canadian mining industry is under immense pressure to compete with foreign mine operations. The very survival of the Canadian mining industry is threatened by lower ore grades, environmental pressures, high cost of labour, unfriendly tax laws toward exploration and the increasing cost of new technology. In order to compete in the world market, Canadian producers and their suppliers are rethinking age old customer-supplier relationships in favour of preferred supplier relationships which can improve the profitability and enhance the competitive position of both partners.This paper attempts to redefine partnerships with suppliers in the context of a ""win-win"" objective. It will outline the measurable benefits to both partners through a representative product which highlights the keynote structure of any successful supplier partnership The Status Quo...Mines all over North America are plagued with the same recurring questions, ""Who has the best product for my operation at the lowest price... How do we know a product will perform to a supplier's projections after the sale...What do we do if the product fails to perform as expected?"" These questions have been asked by underground mining operators for decades but rarely have long-term solutions with measurable results been achieved.The LHD industry is one example of the status quo where partnerships will provide large gains toward technological advancement, reducing mobile equipment costs. The underground mining industry is out of sync with their surface counterparts in the open pit business.Partnerships with suppliers in the open pit world are not only a standard practice but a culture which has existed for decades. Open pit operators enjoy concepts which fix their mobile equipment costs for the life of the mine and hold the equipment supplier accountable for performance and fleet economics for 60 000 service hours and longer.Manufacturers are attempting to transfer this culture into the underground mining industry. Figure I illustrates the significance of a capital driven decision."

Jan 1, 1994

By Jack G. Pippenger

The Coteau Properties Co.'s Freedom Mine is a surface lignite mine that uses large draglines, trucks and shovels, tractor-scrapers and bulldozers to uncover a single coal seam. In 1989, a work order system was instituted to record data by equipment type, cost, productivity and distance. The system was also used to provide historical information to plan the most efficient and economic use of each equipment type in the mining operation. The Coteau Properties Co. is a wholly owned subsidiary of The North American Coal Corp. The company was formed in 1972 to supply lignite from its Beulah-Hazen coal reserve to a coal gasification project and an electrical generating facility located near Beulah, ND. The reserve consists of a single coal seam between 3 and 7 m (10 to 23 ft) thick. The overburden above the coal is predominately glacial tills and clays and ranges from 6 m (20 ft) to more than 60 m (200 ft) thick.

Jan 1, 1994

By Burford B. D, Johnson N. W, Rohner P

Under design philosophy, the Hilton concentrator produced lead, zinc and LGM (lead plus zinc) concentrates. The LGM (Iow grade middling) concentrate was produced by combining coarse middling streams from the lead and zinc circuits, regrinding and subsequent flotation. Mineralogical examination of the zinc circuit middling stream prior to regrinding suggested that production of zinc concentrate from the zinc circuit middling stream should be possible by rearranging existing plant equipment. Laboratory testing of samples of plant products, however, showed that regrinding combined wi th the usual reagent suite was nO1 sufficient to produce a zinc concentrate of the required specifications.Examination of the process water highlighted a problem with dissolved salts in the circuit water, which was solved by in-circuit precipitation of the dissolved ions with soda ash. Implementation of the procedure in the concentrator effectively transferred to the zinc concentrate all sphalerite previously recovered to the LGM concentrate.

Jan 1, 1994

By J. D. Miller, C. L. Lin

A PC, image-based, on-line instrument for measuring coarse particle size on a conveyor belt is under development. The hardware and software required to implement such a system are discussed, including the interface for the special image-acquisition hardware. The system concept is given with examples to illustrate the step-by-step procedure for the implementation of image-processing algorithms.

Jan 1, 1994

By Graham Davis

The future of the world's minerals industries is often painted as bleak. Peter Drucker has repeatedly proposed that the demand for minerals has become "uncoupled" from world economic growth.' This implies that, while mineral demand was in the past linked to the growing demand for and consumption of goods and services, further world development will not require substantial mineral inputs. Lester Thurow noted that for these reasons the US minerals industry is diminishing in scale and economic importance.2 There is some documented evidence of such uncoupling, and the demand for minerals may indeed diminish in the future. But such announcements are, to this point, no more than speculation. For instance, is it not just as likely that renewed environmental concerns will cause increased demand for the relatively innocuous environmental properties of metals, replacing plastics? And even if the prophesied demand decreases do occur, a sufficient fall in metal prices due to technological advances could increase the quantity of minerals demanded above current levels, in spite of leftward shifting demand curves. Thus, worldwide mineral production activity may increase or decrease in the future and no one can say whether more or fewer of the earth's citizens will become involved in the extraction and processing of minerals.

Jan 1, 1994

By B. Das, D. D. Mishra, M. I. Ansari

Experiments conducted with a 75-mm-diem hydroryclone have shown it is possible to obtain an iron ore concentrate containing 60% Fe. 2.65% SiO2, and 4.0% Al2O3 from Barsua iron-ore washing-plant slimes. About 60% of the iron values are recovered from slimes containing approximately 49% Fe, 8.9% A1203 and 11% SiO2. The obtained products can be used in the sinter feed for iron and steel making. The key to achieving process success lies in establishing the correct cut point (d50) of the hydrocyclone through the manipulation of operating and design variables, such as spigot and vortex finder diameter, solids concentration and operating pressure. The cyclone efficiency is represented by the partition curve. The cyclone performance, evaluated mathematically from the reduced efficiency curve, is represented by the equation Y = 100[1 -exp(-axb)], where: •X = did 50, •Y = corrected of efficiency (%) and •a and b are constants.

Jan 1, 1994

By Paul W. Jeran, Michael A. Trevits, William P. Diamond

In this U.S. Bureau of Mines study, production trends have been analyzed for 82 gob gas ventholes on 7 longwall panels in the Lower Kittanning Coalbed, Pennsylvania. Cumulative production from individual holes was found to vary considerably, ranging from 0.03 x 106 to 10.1 x 106 m3. Peak production rates were generally about 0.03 x 106 to 0.06 x 106 m3/d, but rates over 0.10 x 1@ m3/d were observed. The variability of gas production from individual holes can be attributed to several factors, including completion practices and problems, the extent of fracture development in the strata above the extracted panel, water production, and location on the panel. Of particular significance is hole location. Holes on the ends of the panels, where overburden strata are in tension because of the support of the surrounding pillars, were generally the highest and longest producers. This observation led to the experimental placement of gob gas ventholes in the zone of tension along the margin of a panel, instead of in the traditional centerline location, which is in compression. Analysis of 7 months of gas production data indicates that the experimental near-margin holes produced 77 pct more gas than did centerline holes on the same panel.

Jan 1, 1994

By H. T. Mulryan

Talc is used as an essential ingredient in a variety of plastics applications ranging from polyester body patch compounds through polypropylene automotive, appliance and household furniture components to high performance parts made from liquid crystal engineering resins. This paper focuses on polyolefin applications, the three-tier market for talc in polypropylene, the effects of various tales in typical compounds and trends in each market segment. Emphasis is given to emerging markets, examples of which are polypropylene compounds that mimic higher cost resins, and polyethylene films. Customer requirements for tales for these purposes are discussed.

Jan 1, 1994

By D. Zhao

High temperature deformation characteristics of austenitic 304L, and martensitic 410 and 416 stainless steels were investigated by conducting compression tests over a wide range of temperatures and strain rates (950-1250 C and 0.001-20 s-1). Flow behaviors of the three alloys were characterized. Optical metallography was performed to determine the as-deformed microstructures. The flow behaviors were related to microstructural phenomena during high temperature deformation. Dynamic recrystallization was responsible for the flow softening. Both dynamic and static recrystallization were operating, and the recrystallized grain size increased with increasing temperature and decreasing strain rate. Strain rate sensitivity was found to increased with increasing temperature and decreasing strain rate. No defects such as cracking and shear bands were observed at those test conditions. Preferred processing conditions can be selected by considering as-deformed microstructure and strain rate sensitivity.

Jan 1, 1994

By Suresh K. Bhatt

Although overall worker productivity for U.S. underground coal mines is available, productivity by mining method and seam thickness is not. Mining technology has gone through dramatic changes in the past decade, and the industry has experienced a lack of accurate productivity Figures addressing these changes. This information is of great interest in planning for future mining systems as thick and shallow coal seams currently being mined are depleted and exploitation of thinner, deeper, and better quality seams is considered to partially meet the requirements of the 1990 Clean Air Act Amendments. In a cooperative program, the U.S. Bureau of Mines obtained raw mine level production and related data from U.S. Energy Information Administration for 1989 and 1990 and performed the needed statistical analysis. Base criteria, parameters, and salient results of the mine productivity analysis are presented in this report.

Jan 1, 1994

By N. M. Steven, J. M. Moore, J. L. Kuyper

Mineral exploration and research has led to the identification of four types of tungsten mineralization in the NE-trending, Iargelyensialic, inland branch of the late Proterozoic/early Paleozoic Pan-African Damara Orogen. The mineralization (mainly scheelite) occurs in a terrane (the Central Zone) that is characterized by multiple deformation, greenschist/amphibolite-facies metamorphism and numerous peraluminous S-type granitic and pegrnatitic intrusions. The four major types of scheelite mineralization are (in ascending stratigraphic order of host rock): (1) thin (5 cm to 2 meter) quartz+plagioclase+diopside ± scapolite calc-silicate granofels with fmely disseminated scheelite (scheelite-bearing granofels; SBG) developed as discontinuous intercalations within the calc-silicate rocks of the Khan, Spes Bona, Oberwasser and Kuiseb Formations (Nosib and Swakop Groups); (2) gamet+pyroxene± vesuvianite+scheelite ± fluorite replacement skarns hosted by Okawayo, Karibib and lower Kuiseb Formation marbles in the aureoles of late tectonic, unrnineralized leucogranites; (3) metaturbidite-hosted scheelite- (and possibly wolframite-) bearing tourmalinites, both stratiform and crosscutting, in the Kuiseb Formation located in the 'cleavage fronts' of late tectonic granitoids; (4) scheelite-bearing vesuvianite+quartz+garnet skarnoid rocks (several hundred meters in length) in the calcareous metaturbidites of the upper Kuiseb Formation. These scheelite occurrences were discovered by the follow-up of a large number of tungsten anomalies located during a regional stream sediment sampling program. Detailed mapping, ultra-violet surveys and rock sampling proved to be the most effective surface exploration techniques for locating mineralization; soil sampling and geophysics were of almost no use. The largest, continuous scheelite-bearing skarn of economic interest, Otjua, has a drill-indicated reserve of 250 000 tonnes at 0.53 wt5 WO3 and 8 wt% CaF2•

Jan 1, 1994

By Bengt H. Fellenius

Session 2, Deep Foundation without Soil Excavation, has attracted no fewer than 22 papers dealing with subjects from soil improvement by grouting, injection, and deep mixing techniques through vibroflotation and special piles, including aspects pertaining to conventional driven and bored piles. In the short time available, it is not possible to both do justice to the papers and provide a critical review of the state-of-the-art. Instead, to meet the objective of making the next half hour worthwhile to the audience, I have chosen to comment on a few special points brought forward in the papers and thereafter to discuss more in detail a couple of aspects I have deemed to be of general interest. Four papers deal with jet-grouting, injection, and deep mixing techniques: DOMSKI, J. J. Reinforcement of subsoil under the foundations of historical buildings in Cracow using deep injection technique. RESTELLI, A. B, BERTERO, M., and LODIGIANI, E. Deep mixing technology to improve the bearing capacity of a very soft clayey soil under an earth embankment.

Jan 1, 1994

This United States Bureau of Mines study is based on a review of U.S. mine fire accidents that occurred from 1970 through 1989. Information on these accidents was obtained through investigative reports written by Mine Safety and Health Administration personnel. For this study, 260 mine fire accident reports were examined. A previous Bureau research effort established that fires causing fatalities were more likely to occur in haulage entries than at any other underground location. This study has found that the most prolific source of haulage entry fires was the inadvertent grounding of trolley wires. The largest segment (15 out of 40 trolley wire fires) resulted from not maintaining adequate clearance between the trolley wire and the vehicle. Several novel fire prevention and control ideas have evolved in response to frequently occurring fire-related problems. These included; discriminating power isolation devices, wire cutting devices, more accessible fire extinguishers, vehicle overcurrent protection, and vehicle fire suppression.

Jan 1, 1994

By Rustu S. Kalyoncu

Rainbow colors of roofing granules, adorning the roofs of buildings from single family units to largest office buildings, have their origin in the roofing shingles as burlap soaked with tar appearing as early as the 1700s. Dusting of talc and mica on the coated surfaces, to keep roofing from sticking to itself in storage, represents an early improvement to the original construction product. Sometimes, colored, natural mineral dusts were added as color pigments within the dusting material, for initial color. Prolonged exposure to sun caused the asphalt to become brittle, and it eventually cracked and leaked. Search for solutions to cracking and subsequent leaking problems eventually led to the use of crushed mineral granules on asphalt coated shingles. This provided the impetus for further growth in the asphalt roofing industry. Application of a layer of crushed mineral on the asphalt coating minimized the coating deterioration from exposure to ultraviolet light, thus significantly improving the shingle life. In the 1900s, screened waste from slate quarries was the most commonly used granule in asphalt roofing products. Records indicate the use of coarse slate screenings for asphalt roofing as early as 1906. As the asphalt roofing industry further developed, other naturally colored minerals, such as silica sand, quartz, mica, feldspar, talc, slag, granite, rhyolite, and oyster shells were used on roofing surfaces. Later on, a number of manufactured granular materials, such as crushed brick and tile, fire clay, and white porcelain were used. The first artificially colored roofing granule was produced in 1914 by running molten slag into a solution of alkaline metal silicate, which was absorbed by the porous slag. Various colors were obtained by adding pigments to the silicate coating and by subsequently heat treating the granules. In 1922, another technique was developed in which green slate granules were saturated with copper sulfate solution and heated to 760°C to form copper oxide. Since then, many other granule coloring processes have been patented, one of the most significant being the sodium silicate coatings introduced around 1975. Granules as used in construction (specifically roofing materials) are defined as natural or synthetic-mineral grains smaller than gravel and larger than sand in particle size. They are used primarily for protective and decorative purposes on the weather- exposed surface of asphalt composition roofing. Development of artificial coloring techniques has made it possible for the roofing industry to provide asphalt roofing shingles in a wide variety of colors complementing the color and style of buildings. Roofing granules, as we see today, are the products of long technological evolution.

Jan 1, 1994

By Brian Lightfoot

Ausmelt technology is a versatile bath smelting technology with application in many waste treatment fields at low capital and operating cost. Heavy metals extracted from wastes may be recycled to mainstream use and the slags produced will be inert and suitable for use as aggregate, shotblasting grit or other applications.

Jan 1, 1994

By R. Grant, C. Bazin

"Brunswick Mining has investigated grinding media optimization for the purpose of improving the flotation feed and regrind product size distributions to enhance metal recoveries. This paper presents the findings of on-going testing of various sizes and shapes of grinding media. Plant observations combined with estimated breakage rates demonstrate the importance of appropriate selection of media sizes on the milling operation.IntroductionBrunswick Mining and Smelting is located near Bathurst, New Brunswick, and operates one of the world's largest lead and zinc mines. The ore mineralogy and processing flowsheet have been described elsewhere (Petruk and Schnarr, 1981; Shannon et 01., 1993). Despite the 25 years' milling experience, there has been considerable disagreement as to the required grind size (Grant et 01., 1991). Since 1964, fineness of the flotation feed ranged from 60% to 80% passing 400 mesh (37 um) and averaged slightly above 71% in 1992. Results from mineralogical analysis (Petruk and Schnarr, 1981), laboratory and pilot plant experiments, as well as plant sampling (Grant et al., 1991; Hendriks and Ounpuu, 1985; Shannon et al., 1993) indicate that improved metal recoveries can be achieved by an increase in the fineness of grind, and more specifically by maximizing the amount of material in the 15 urn to 25 um range.This paper shows the results obtained so far from the evaluation of the effect of grinding media size and shape on grinding mill efficiency. The problem of finding optimum grinding media size, shape and composition has been recogrtized since the early 19405. The main criterion for the selection of media size is the size of the material to be ground (Bond, 1958). Although several relationships have been proposed to assist in the selection of grinding media size, none of them are entirely satisfactory (Wills, 1988). Other approaches using the breakage rates and process simulators were developed to help in the selection of grinding media size (Austin et al., 1976; Lo and Herbst, 1986; Concha et 01., 1992; Samskog et al., 1990; Martinovic et al., 1990). Although considerable effort was put into the analysis of grinding media size, very little information is available on the effect of grinding media shape (Norman and Decker, 1985, p. 3C-4). Norris (1952), Kelsall et al. (1973) and Herbst and Lo (1989) have shown that balls are more efficient than other shapes of grinding media including truncated cones and cubes."

Jan 1, 1994

By Semple DG, Leach TM

A continued exploration programme has further defined the geology of the Tolukuma vein system, verified the resource indicated by Newmont, and identified potential for additional mineralisation. The resource at Tolukuma Hill, designated as Zone C, is a measured 440,000t @ 17g/t Au and 46g/t Ag with an additional indicated resource of 120,000t @ 16g/t Au. A diatreme breccia localised at an intersection of structures, and a relationship of gold to base metal sulphides, are highly indicative of a porphyry association. Typical epi-thermal features such as crustiform banded quartz and quartz pseudomorphing. platy calcite are also present and locally contain lesser gold mineral-isation. Pre-existing dilatant structures have acted as a host to the ore fluids, resulting in the formation of the semi-continuous Tolukuma-Gulbadi veins over a 1100m strike. A fluid flow model suggests that mineralising fluids were sourced from the diatreme margins and migrated laterally along dilatant structures. Bonanza gold grades are derived through fluid quenching in the flexure between a hanging wall split which hosts much of the Tolukuma Hill resource and the feeder graben structure. Thus, the relationship between the pre-mineral structural geometry and fluid upflow at the margins of a diatreme breccia, controls the ore setting. Potential for more ore remains within the Gufinis and the 120 veins as well as in the outlying Prospects.

Jan 1, 1994