1. DIAMOND MINING.

    GEM AND ROCK VENTURES CO. LTD. has been undertaking gemstones (mainly tanzanite) mining, trading in gemstones, lisensed, diamond dealers and lapidary workshop.

    That of late GEM AND ROCK VENTURES CO. LTD. has decided and resolved to expand its mining business and in particular in Diamond prospecting, Mining and Trade.

    Though the company has been dealing with Diamond buying and selling, this was a very small scale.

    The company has found that it is now high time it expanded its diamond business not on buying and selling but also mining the same.  Thus the Company has acquired some mining plots in Shinyanga Region for that purpose.  It intends to acquire more mining plots in other areas within Tanzanite.

    DIAMOND INDUSTRY IN TANZANIA

    •    Diamond production in East Africa is totally limited to the shield area of Tanzania just South of Lake Victoria principally in the Shinyanga Region.  The famous Diamond mining well known in Tanzania is the Williamson Diamond Mining, of late known as Mwadui Mining Company.
    • Diamonds have also been mined in Tanzania from five other area in Shinyanga Region which include Mabuki Mine in Kwimba District, Kisumbi Mines, Usongo Mine and Uduhe or Premier Diamond Mine located in Maswa District.  A fifth deposit is that of Kahama pipe.  There is also a large Kimberlite pipe on the western area of Singida Region.
    • That Williamson Diamonds Ltd. also established a lapidary industry in Iringa which was well known as Iringa Diamond cutting Industry.  Thus diamonds were cut and polished before being exported to other countries.

    GEM AND ROCK VENTURES LTD. has a lapidary workshop in Arusha Tanzania.  With the expansion of business to Diamond Mining it will create more jobs and more profit for the company.  However in order to enter into Diamond Mining the Company need more funds for buying modern mining equipments.

    PROSPECTS:

    • GEM AND ROCK VENTURES CO. LTD. prospects in Diamonds mining are very high.  As per the history of Diamonds mining in Tanzania has it, diamonds were first discovered in Tanzania at Mabuki, which is approximately 60 kilometres Southeast of Mwanza on the Sourthern shores of Lake Victoria just before the beginning of the First World War.
    • Tanzania’s serious entry into diamond business began in 1940 when Canadian geologist, Dr. John T. Williamson discovered rich diamond bearing gravel in association with a kimberlite pipe at Mwadui, 19 kilometers Northeast of Shinyanga.  Since then diamond business in Tanzania has been expanding though at a low pace.  Thus to – date Diamons have been by far the most valuable of Tanzania’s mineral export.  Tanzania diamonds are spectacular due to their beautiful pink colour as evidence by the Williamson and De Young, diamond experts.  Thus Diamonds business in Tanzania have very high prospects.

    GEM AND ROCK VENTURES CO. LTD. thus invites interested companies, individuals etc. to join them in this business.  The Company is ready to expand its company by increasing its shares and/or enter into joint ventures and/or partnership with any foreign and/or local companies.

    GEOLOGY

    Kimberlites have been found throughout Tanzania, but they are principally clustered in the Shinyanga, Nzega, and Singida – Iramba regions in the Precambrian rocks that make up the geologically stable central shield of Tanzania (Edwards and Howkins 1966). Their age is a matter of debate.  They are generally believe to be at least 2 billion years old.  However, five kimberlites have been discovered in the southern province of Tanzania, where they intrude the Jurassic karroo sediments (thus they are younger than these sediments) and are said to form spectacular outcrops as evidenced by aerial photographs (Edwards and Howkins 1966). More than two hundred kimberlite occurrences have been recognized by Edwards and Howkins (1966) as occurring in ten provinces: (1) Speke Gulf, (2) Shinyanga, (3) Kimali, (4) Nzega, (5) Singida – Iramba, (6) Nyahua River, (7) Saranda, (8) Bahi – Kisigo River, (9) Rungwa River, (10) Ruhuhu River. Of these, only the Shinyanga Province has produced diamonds, and here, only the Mwadui pipe has been significant.

    Underground development of the Mwadui Mine has yielded a great deal of information about the pipe.  Sharply defined contacts between the kimberlite and the surrounding country rock are commonplace. It is noteworthy that alteration of the surrounding country rock is extremely limited, suggesting that the kimberlite was emplace at relatively low temperatures. In contrast with the crater margin at the surface, no breccia zone occurs between the kimberlite pipe and the country rock on the mine’s 400 meter (1,200 – foot) level.

    At the Mwadui pipe, most of the production has come from overlying superficial residual deposits and more tha 900 feet deep that represent millions of years of erosion and diamond reconcentration. The material in the crater consists of shaly sediments, indicating the presence, in the past, of at least one crater lake. Below the sediments is the kimberlite pipe itself. According to Edwards and Howkins (1966), within the pipe three distinct varieties of kimberlite have been recognized: (1) kimberlite tuff, (2) porphyritic primary kimberlite, (3) fine – grained primary kimberlite.

    Other geological units associated with the Mwadui pipe were worked out by Harris (1961). He reported the following sequence:

    		 Black soil (mbuga clay)                      Superficial  deposits

    Red gravel                                         Zone 1
    Calcareous gravel                                             approximately 3-10metres

    Silcrete gravel                                      (10 – 30 feet)

    Silcrete

    Shale                                                    Zone 3

    Transition – zone rocks                                    approximately 50 meters   (150 feet)

    Kimberlite A, lapilli tuffs

    Gray sediments                                                                  Zones 4

    Transition – zone rocks                                    approximately 140 meters                                                                              (500 feet)

    Kimberlite B, green lapilli tuffs

    Granite breccia with minor          Zone 5
    Kimberlite                                 thickness unknown

    Kimberlite C, igneous breccia             Zone 6 thickness unknown

    A marginal zone of brecciated granite gneiss adjacent to the pipe is known as Zone 2.

    According to the mine geologists, the 650 feet of material in Zone 3 and 4 is comprised of tuffs deposited as volcanic cones but partially reworked and the water – laid sediments derived from them. The tuffs, which are referred to as kimberlite A and B, are well – bedded deposits containing numerous large boulders of country rock, they do not have the appearance of typical volcanic tuff and agglomerate and may be water – laid sediments derived from kimberlite C, an igneous breccia.

    The superficial deposits have been extremely productive in diamonds and make up several million tons of the proven ore reserves. Exploration of the kimberlite A of Zone 3 to a depth of 40 meters (130 feet) has shown values of 10 to 14 carats per hundred tons, a large volume of this type of material is though to exist. The kimberlite B of Zone 4 and kimberlite C of Zone 6 may also be worthwhile but have not been explored.  The known ore reserves are sufficient to assure the life of the mine for several years to come.
TANZNITE:-

Mining of Tanzanite gemstones is undertaken at the Merelani mines about 50kms from Arusha. The area is accessible by road


 

  

We do own and operate our own mines. Our participation is limited to close collaboration with small and medium scale miners in Merelani by providing limited support in financing and in providing technical assistance. This relationship with large numbers of small miners gives us easy and first hand access to mine products.