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Rocks, Minerals, and Crystals of the Orange River/Gordonia Pegmatite Belt
You are here: MineralCollecting.org >> Posted Articles >> Article 40

Submission Id No.: 200509230000026647
Submit Date: 2005/09/23
Submit Time: 15:56:13
Name: Crystal Spring Minerals
Email: queries@crystalspringminerals.net
Article Title: Rocks, Minerals, and Crystals of the Orange River/Gordonia Pegmatite Belt
Article Content:

Climate and Environment
The average rainfall for this region is recorded as 90mm - 127mm per annum. Only thing is, this records is for the full period of time that it has been measured and do not mention that all this precipitation occurred once in 3 - 4 years, leaving the other years with zero rainfall. Summer temperatures are extremely high, 47 Degrees Celsius; with Goodhouse reaching temperatures of well above 50 Degrees Celsius. Short spells of cold weather, The vegetation is typical that of a semi-arid region with various types of Euphorbia, hardy stunted shrubs and giant quiver trees in places. Although grass is scarce it flourishes after rainstorms on the sandy flats. In the heart of this harsh, barren dessert land, the life giving Orange River makes it's way through the dry land, and nurse a narrow, green, vegetated line alongside the river. The Karoo and the arid Richtersveld owe their characteristic features to the underlying of this particular region.

Minerals and pegmatite belts of the region
The first geological survey, conducted on the Gordonia pegmatite belt was conducted in 1959. The pegmatite belt South of the Orange River in Namaqualand was done in the early thirties. Goodhouse and the area between Riemvasmaak and Kakamas was mapped in 1941 to 1946. Although the Pegmatites between Goodhouse and Onseepkans bare almost no minerals, it yields the most spectacular rock crystals. Numerous pegmatite belts occur in the North Western part of the Northern Cape and form lengticular and dyke-like bodies of variable size. The largest of the these stretches over 200km and runs through Kenhardt and Kakamas to end in the confluence of the Molopo- and Orange Rivers. A second stretches along the Orange River, on both South African and Namibian sides, from where it start; east of Onseepkans crossing Pella, Witbank, and ending West of Goodhouse. Another import and pegmatite belt occur to the South of Vioolsdrift including the Noumas I and Noumas II pegmatite, also known as Blesberg or "Jiveberg" as the locals refer to it. There were two phases of pegmatite intrusion on this pegmatite field, the older; being 1 000 million years and the younger; 950 million years ago. The two latest mentioned pegmatites are the only worth to elaborate on about mining activity.

- Blesberg/Noumas I and Noumas II pegmatite
Situated 15 km Sough of Vioolsdrif, it is the largest known mineralized pegmatite in the Namaqualand. It is mined mainly for feldspar, but also yield Barel, Bismuth and Tantalite/Coloumbite. Smoky quartz is common for this locality, but because it is mined for the feldspar, and the quartz occur within the feldspar, the use of heavy machinery and explosives limits the amount of specimens from Blesberg.

- Aggeneys pegmatite
Situated 60km West of Pofadder and 35km South of the Orange River it is mined for Lead and Zinc. Specimens from this locality is very hard to come by, because of explosives and heavy machinery used.

Most of the large pegmatites originated through a process of replacement during the final phases of crystalization. This happened in different phases and formed successive layers of crystals deposited against the walls until the pegmatite chaimber becomes completely full. This explains the iron oxide and chlorite inclusions that is a characteristic of quartz crystals from this region. But don't be mislead by the vast area that is covered by this pegmatite field. The phantom crystals that the world has come to know as Orange River quartz, makes out only a very small quantity of the quartz crystals that is found in the region. Most, I will dare to say, about 90 % of all the quartz crystals found in the region are large pale, milky quartz with no luster and has brown-grey hematite/iron oxide included. These don't appeal to anyone except the few garden enthusiasts that also fancy crystals. But in fact, about 90 % of the quartz on pegmatites didn't form crystals at all, and occur as large bulky quartz ridges of a milky white colour known as pegmatites. The most interesting aspect about Orange River Quartz is the vast amount of colours that it occur in. White, grey, red, purple, pink, orange, brown, black and yellow colour is all caused by iron/hematite. Green is caused by chlorite in each and every case I came across it. These colours are trapped inside the crystal and the result of multiple phase crystal growth. Of the few localities in the world that produces red or any other coloured phantom quartz, like China and Madagascar, the Orange River quartz has the most constant colour. It is praised by crystal healers for its great energy. Single crystals makes out great material for wire wrapped jewelry and cluster specimens of Orange River quartz are highly sought after in collector circles.

Crystal Spring Minerals
www.crystalspringminerals.net
P. O. Box 289
Kakamas
8870
Norhern Cape
South Africa

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