Alluvial sands

A Virgin gold in golden veins is every gold digger s dream. Mostly, river-worn nuggets had to be tediously sorted from alluvial sand. 

A third profile (BRAC 1) was examined beneath Late Miocene alluvial sands and ferruginous gravels. This profile is considered to be mid Cenozoic in age and has been partly eroded. The upper part of this profile below the unconformity has a similar REE pattern to NASC. Deeper in the profile there is relative enrichment in all the REE, but slightly more marked in the light REE (Fig. 4). 

Although platinum occurs as grains and nuggets in the alluvial sands of many rivers, there is only slight evidence of its use by ancient peoples. The pre-Columbian Indians, however, near the place now known as La Tolita, Esmeraldas, Ecuador (39), produced white alloys of gold and platinum, from which they made many little artifacts, some of which are now preserved in the University of Pennsylvania Museum in Philadelphia and the Danish National Museum in Copenhagen. Since plati-... 

Alluvial sands, glacial tiU, and lake sediments typically contain <1-15 mg kg arsenic. Stream sediments from England and Wales had a median arsenic concentration of lOmgkg (Webb, 1978). The median arsenic concentration in stream sediments from 20 study areas across the USA collected as part of the National Water-Quality Assessment (NAWQA) program was 6.3 mg kg (Rice, 1999). 

Figure 3.8 Examples from the ferricrete alteration profile observed at outcrop at Palika Ba (13°28 N, 15°14 W), near the Gambia River, Gambia, West Africa. (A) Nodules of ferricrete developing within Quaternary alluvial sands and silts deposited by the Gambia River. Nodules consist of predominantly goethite with minor haematite (sample PG4 in Table 3.3). (B) Massive iron-cemented ferricrete horizon displaying characteristic tubes (i.e vermiform structure sample PG2 in Table 3.3). Importantly, the iron cement is entirely due to the introduction of allochthonous iron into the pore spaces of the sediment.

Bedrock units are mantled in some areas by 3—15 m of Quaternary terrace deposits consisting mainly of sand and gravel. Along the principal rivers and streams of the region, alluvial sands, silts and clays commonly are 5—20 m thick. 

Occturence.— Free in its three allotropic forms The diamond in octahedral crystals in alluvial sand, clay, sandstone and conglomerate graphite, in amorphous or imperfectly crystalline forms amorphous, in the different varieties of anthracite and bituminous coal, jet, etc. In combination, it is very widely distributed in the so-called organic substances. 

Gently sloping to level, loose to medium dense, alluvial sand. Relative density varying between 50% and 70%... 

Medium to fine sand varying from loose (N < 5) sand at surface to dense (N = 50) sand at 85 ft Level loose (N = 5) fine-grained alluvial sand. Relative density 50%... 

Level hydraulic backfill composed of loose alluvial sand (average N-value c 6)... 

Silty sand, gravelly about 20% hard, angular gravel particles 12.5 mm maximum size rounded and subanguiar sand grains coarse to fine, about 15% nonplastic fines with low dry strength well compacted and moist in place alluvial sand (SM)... 

Identify that the most unstable are soils it is alluvial and lake-marsh loam and clay, and loam and clay with flow index in the range 0.50 0.75 and 0.75-1.00 as well as alluvial sands small and medium-size, medium-density saturated with water. This category also includes technogenetics made soil. 

Engineering-geological layers which are steady, are composed of alluvial sand small and medium size and solid build and of sand with inclusions of gravel and pebble. In this category there are the layers presented by weakened organo-mineral soils (silt), and alluvial loams and clay with an indicator of fluidity of in the range of 0.75-1.00 and 4 > 100. It is explained by the area of development of these layers, and also conventionality of the chosen methodical approach to establish such relations. The thickness of wave-built soil (layer 1), developed in the south-eastern part of the site is also relatively stable. 

This encompasses a single area whose flora is related to the sandy pediments that extend from south-eastern Piauf to western Pernambuco and northern Bahia on alluvial sands. This flora has... 

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