Sluice Box Research Articles

Effects of Suction Dredging on Streams: A Review and an Evaluation Strategy

Abstract Suction dredging for gold in river channels is a small-scale mining practice whereby streambed material is sucked up a pipe, passed over a sluice box to sort out the gold, and discarded as tailings over another area of bed. Natural resource managers should be concerned about suction dredging because it is common in streams in western North America that contain populations of sensitive aquatic species. It also is subject to both state and federal regulations, and has provided the basis for litigation. The scientific literature contains few peer-reviewed studies of the effects of dredging, but knowledge of dredging practices, and the biology and physics of streams suggests a variety of mechanisms linking dredging to aquatic resources. Effects of dredging commonly appear to be minor and local, but natural resource professionals should expect effects to vary widely among stream systems and reaches within systems. Fishery managers should be especially concerned when dredging coincides with the incubat...

Improving the simple sluice box

The simple sluice box which has been in use for thousands of years for the recovery of heavy minerals, notably gold, is a complex system in terms of the physical mechanisms operating in the box and not well understood. The challenge is to improve the recovery of fine heavy mineral in the sluice box. The study described in this paper has increased our understanding of the mechanisms operating and in particular has established the importance of the behaviour of the settled gangue layer in the box. It also describes how the design of a sluice box can be modified to improve its effectiveness so that both grade and recovery of fine material can be improved.

The Knelson concentrator. metamorphosis from crude beginning to sophisticated world wide acceptance

Byron Knelson is the inventor of the centrifugal concentrator that bears his name. His initial involvement in mining was through an investment in a Yukon placer mining project and a seven day visit to the site. This brief exposure inspired a search for a better and more scientific recovery system than the sluice box and longtom that dominated the industry in 1970. His story depicts his search and the development of the device that has virtually revolutionized gravity recovery. The logic behind the Knelson design is compared to the single wall centrifugal concentrators of earlier and latter years that have had singularly unimpressive acceptance by the industry. This is due to their inability to sustain concentration of values for more than a few minutes before serious losses occur. The unsolicited case studies of Knelson installations provided by a number of hardrock and base metal operators are mentioned. These case studies lend positive proof to the economic advantages of installing Knelson concetrators in gravity circuits. Over 750 Knelson equipment installations have been made in over 50 countries. Twelve different models of concentrators are presently fabricated in the Knelson operated factory. These models include a 3“ laboratory concentrator and 7.5” exploration and/or reconcentrator model for upgrading the concetrate produced by 12”, 20” and 30” production models which are capable of sustaining up to 40 TPH solids. Options include fully remote computerized operation, stainless steel wetted surfaces and centre line concentrations discharge. Continuously operating concentrators are being developed for base metal recovery and the benefication of coal. Test installations are presently being operated at a Canadian iron ore mine and a coal processing plant in Australia. A third installation will take place shortly at the Canadian Coal Research facility at Devon, Alberta.

Elimination of hydraulic effects for cassiterite in a Malaysian Stream

Geochemical patterns for elements, such as Sn, W and Au, present in drainage sediments as resistate heavy minerals are often erratic and difficult to interpret. To investigate the source of these problems and develop methods of eliminating them we have compared the behavior of Sn, present as cassiterite, and associated pathfinder elements downstream from a small primary Sn deposit in Perak, Peninsular Malaysia. Dispersion trains for the pathfinder elements are characterized by smooth decay patterns and differences in concentrations between high- and low-energy environments, characterized by coarse-and medium-grained sands respectively, are not significant. In contrast, Sn (and magnetite) concentrations are extremely erratic with significantly higher concentrations in high- compared to low-energy environments. As a result the dispersion train for Sn exhibits no regular decay pattern away from its source. These findings suggest that the action of the stream is analogous to that of sluice box, with light minerals being winnowed away and cassiterite, together with magnetite, accumulating. For all but the finest sizes this process, which is most efficient in high-energy environments, causes considerable local variability in Sn content of the sediments. However, because the hydraulic behavior of cassiterite and magnetite is similar, but magnetite is not associated with the primary mineralization, the Sn/magnetite ratio can be used to eliminate Sn anomalies resulting from local variations in hydraulic conditions. The concept of hydraulic equivalence of cassiterite and magnetite was extended to examining the relationship between Sn and different size fractions of the light minerals that constitute the bulk of most sediments. Greatest contrast is obtained when the Sn content of the −270 mesh (−53 μm) fraction is re-expressed as its hydraulic equivalent concentration in −65 + 100 mesh (−212 + 150 μm) material. For exploration purposes it is concluded that: (1) providing cassiterite is present in the fine size fractions, sampling of this material will reduce hydraulic effects, thereby reducing data variability, and can also increase the length of the anomalous dispersion train; and (2) hydraulic effects can also be reduced by re-expressing Sn concentrations as ratios to magnetite (provided this is not associated with the primary Sn mineralization) or a hydraulically equivalent size fraction of the light minerals that constitute the bulk of the sediment. Similar principles probably apply to the interpretation of geochemical data for other elements dispersed in drainage sediments as heavy minerals; this warrants further investigation.

THE POPULATION SYNDROMES ON THE COLORADO PIEDMONT

The changing population geography of the Colorado Piedmont is the geography of the water resource generated in the proximal southern Rocky Mountains. River water was channeled into irrigation canals from the early miners’ sluice boxes; combining water and land signaled victory over a near-empty land, and an immense machine-labor-intensive agricultural sprawl emerged on the Piedmont landscape. New opportunities have been recognized since 1950, and new resources have been activated. Electronics, research programs, and missile industries requiring a sophisticated scientific environment have been added to the agricultural environment. Large agglomerated populations are thrust onto the landscape, creating a vast urban sprawl and an ever-increasing demand for water. But since there is no additional water available, Piedmont residents must soon decide the differential value of water to agriculture as opposed to water for urban use, and they must decide how soon to sanitize the drainage basins to enable the reuse of water in both usages to permit future growth. I do not wish to engage your attention to all things which bear watching, but there is one more shibboleth on which I wish to comment, and that is the doctrine that education should proceed from that which is immediate to that which is remote. In geography we should begin with our own backyard, then study the backyards of our neighbors, and so on until we comprehend the backyards of the whole world.1

THE GOLDEN ROCK WATER DITCH

I^Sn feverish extravagance of first few years after igfiEHj discovery of gold in many of richer ' jgjQlll mines were soon exhausted. Much untouched ground still remained, however, in areas that were capable of yielding a profit when an adequate supply of water was available. As mining methods developed from pan, batea, and arrastre through cradle, rocker to long torn and sluice box and finally to hydraulic mining, there was an ever increasing need for larger supplies of water. In his article, History of Mining and Milling Methods in California, C. A. Logan rightly observes that, just as the action of water had been chiefly responsible for formation of rich placer deposits of gold sought by pioneers, so was it also the principal agent used by them in winning gold.1