“Granite 71” was the name given to a geological symposium, international in scope, that was held in Rhodesia over a three-week period, beginning on 30th August, 1971. The symposium was organized by the Rhodesian Branch of the Geological Society of South Africa, and 250 delegates from all parts of the world participated and 50 professional papers read. The “Granite 71” postage stamps are being issued to commemorate the occasion.
Granite is one of the commonest rocks of the earth’s crust. It is a medium-grained rock composed
essentially of quartz, feldspar, and mica. However, granites are not the simple uniform mass that the geological map suggests. They comprise a variety of rock types formed by different processes and at different periods of time.
The deliberations on the granites, gneisses and related rocks of Rhodesia covered a wide field. The origin of granitic rocks is an issue of lively debate and the problems of emplacement, structure, mineralogy, chemistry and radiometric ages, which range from over 3 400 million to 1 800 million years, were discussed. The relationship of granites to mineral occurrences of economic importance is significant and the congress, though largely devoted to academic topics, stimulated interest in the search for ore deposits.
Details
- Date of Issue: 30 August 1971
- Date Withdrawn: 9 February 1972
- Date Invalidated: 9 February 1975
- Designer: From photographic studies by University of Rhodesia and Department of Geological Survey
- Printer: Mardon Printers (Pvt.) Ltd., Salisbury, Rhodesia
- Process: Lithography
- Paper: Chromo with brown gum
- Watermark: None
- Perf: 14.5 (comb)
- Cylinders:
- 1A (Black) 1A (Magenta) 1A (Yellow) 1A (Cyan)
- 1B (Black) 1B (Magenta) 1B (Yellow) 1B (Cyan)
- Sheet: R5 x10 (50)
- Quantity:
- 1,000,000 (2½c)
- 400,000 (7½c)
- 250,000 (15c, 25c)