Sftf SSSmSKBS. ■ ISSÏÏv - , 
WORKING GROUP 9 
ATKINSON-BROWN 
491 
It occurs alone or in association with other trees, but its ease of identification 
on 1 : 20,000 airphotos is not known. 
The laterites are of several types sometimes being closely associated with 
quartz gravels. Thus, the useful deposits range from quartz gravels through 
laterised quartz gravel to quartz laterite, laterite gravel and laterite with no 
quartz. Some of the softer laterites are usable, but generally the lateritie clays 
developed over the dolerites are of no value as construction materials. A 
stripping ratio of 1 : 1 for overburden laterite is used in conjunction with haulage 
distance and availability of other materials to determine the economics of 
excavation. Overburden is blade-bulldozed off and stockpiled for subsequent 
infilling, the laterite or gravel is loosened by ripping and the extraction is by 
means of a bulldozer. 
It is considered that, using the criteria described and demonstrated on the 
photographs, a good degree of success in the location of deposits has been 
attained and that by extending these methods in similar areas, better results 
could well be achieved. 
Ackno wledgem ent 
Grateful acknowledgement is made to Mr. J. H. Durr, C.B.E., Commission 
er of Roads and Road Traffic, S. Rhodesian Government and to the Directors 
of Hunting Technical Services Limited for permission to publish this paper; 
to Dr. F. J. Amm, Chief Mining Engineer, Mines Department S. Rhodesian 
Government for geological information and to the Road Research Laboratory, 
D.S.I.R. England for helpful discussions and criticisms. 
References 
1. Brown, N. B. Notes on the Location of Liatertic Road Materials. Unpubl. report to 
Central Road Lab., S. Rhodesia. 
2. Milne, G. Some Suggested Units of Classification and Mapping Particularly for E. Afri 
can Soils. Soil Res. 4: 183-198. 1935. 
Milne, G. Composite units for the Mapping of Complex Soil Associations. Trans 3rd Int. 
Congr. Soil Sci. Oxford. I 345-347. 1935. 
3. Precott, J. and Pendleton, R. Laterite and Lateritie Soils. Commonwealth Bureau of 
Soil Sci. Techn. Comm. 47. 1952. 
4. Mohr, E. and van Baren, F. Tropical Soils. Chaps XII and XVI, 1954. 
5. Amm, F. J. Unpubl. geological map and field notes. Sheet 1731 Do. Geological Survey 
Dept., S. Rhodesia, 1953.