Stones used in Zimbabwean sculpture are locally sourced. Zimbabwe literally means "house of stone", and the country boasts an astonishing diversity of hard rocks that are used for carving, with colloquial names that convey the intrinsic beauty of the medium: green and lemon opal, fruit serpentine, multi-coloured cobalt, semi-precious stones such as purple lepidolite, verdite and dolomite and the lustrous black iron serpentine called springstone. These dense stones have extremely fine grains and uniform structure, making them ideal for expanding sculptural innovation and showcasing the technical skill of the artists.
The majority of stones used in Zimbabwean sculpture belong to the geological family of Serpentine. They are sedimentary, having originally been laid down on a sandy seafloor, and metamorphic, since subsequent exposure to intense heat and pressure over hundreds of millions of years has transformed them into hard stone. Serpentines are rich in iron, so when the stone weathers it turns a rust colour. Serpentine colours range from yellow and green, through brown to black. Serious sculptors prefer the hardest varieties of serpentine such as Springstone, Fruit Serpentine and Leopard Rock. These dense stones have extremely fine grains and uniform structure, making them ideal raw materials for sculpting.
This stone is capable of the most amazing finish that shines to a black luster resembling the black opal. Not surprisingly, its extremely fine finish and excellent durability and hardness make it highly sought after. Mine in Guruve in the north of Zimbabwe, springstone is one of the hardest and darkest stones. It gets its name because of the deposits of iron found in it. The local name was given due to its reputation during the carving process. One of the most famous 1st generation carvers, John Takawira, was said to have coined the name 'springstone' when he tried to carve the stone and it was so dense and strong that the chisel sprung off the stone, hence the name 'springstone'.
Springstone can often be found covered with a thick outer layer of reddish/brown oxidized iron which is inherent in its chemistry. This softer brown infusion can be used by artists to give a sculpture a beautiful two-tone effect, adding to its appeal. Springstone is rated between 5.0 and 7.0 on the Mohs Hardness Scale.
Cobalt is an exotic stone that lends its beauty to the simplest and most extraordinary forms. It is a serpentine variety and can be found in many colours although it is often purple with yellow and white striations throughout. Cobalt is the local name used by Zimbabwean sculptors. There is no actual cobalt in the stone which is mined mainly in Guruve. Cobalt has a hardness between 5 and 6 on the Mohs Hardness Scale.
Opalstone is a variety of the geological family of Serpentine. Artists value the subtle, almost translucent beauty of Opalstone which is further enhanced by uniform shades of soft colours. It is a hard stone known for its extremely smooth, close grain texture with fewer colour variations that other Serpentines. It can be polished to display a high gloss finish.
One of the most prized types of Opalstone found in Zimbabwe is Green Opalstone found in Chiweshe, two hours north of Harare. It is subsequently referred to as Chiweshe Serpentine and was only discovered around 1989. The vivid green colour is predominant, but the stone can range from milky light green to orange coloured iron deposits, browns, fire-reds, blacks and sometimes mottled or specked with red, orange, or bluish dots and patches. Opalstone measures between 5.0 and 5.5 on the Mohs Hardness Scale.
A strikingly unusual verity of Serpentine stone. Leopard Rock is a beautifully coloured stone with pock marks similar to a leopard, hence the name, of yellow and black. These are inclusions of the ferromagnesian mineral, olivine. Leopard Rock is an olivine rich serpentine (known geologically as dunite) which forms part of a serpentine complex 2.6 billion years old. The only known deposits of Leopard Rock are in Zimbabwe, mine in Ruwa near Harare and in a few small mines in Nyanga, eastern Zimbabwe.
It is a very difficult stone to carve and only very skilled sculptors will attempt this stone. Leopard Rock, when polished, has a beautiful glazed finish. Leopard Rock has a hardness between 6.0 and 7.0 on the Mohs Hardness Scale.
FRUIT SERPENTINE STONE
The name 'Serpentine' comes from the perceptible association between the intrinsic texture and patters of the stone and the characteristics of a serpent's skin. The stone boasts an array of colours and no two stones are exactly alike, each given a distinct appearance by the unique pattern of mineral inclusions with the stone. Formed around 2.6 billion years ago, serpentine stones contain quartz, chromium, manganese, copper and iron minerals.
Fruit serpentine is a harder variety of serpentine, beautifully multi-coloured with deep veins of variated strata. Fruit serpentine comes form the Kwekwe area, a few hours southwest of Harare and is also referred to as Kwekwe Serpentine. Fruit Serpentine has a hardness between 4 and 5 on the Mohs Hardness Scale.
Skilled artists in Zimbabwe can also carve stones that are not in the serpentine geological family, including Lepidolite, Dolomite and Verdite stones.
Lepidolite is a stunningly beautiful, semi-precious stone presenting itself in various shades of soft lilac, mauve and purple. Occasionally, lepidolite contains streaks of white, yellow or grey. Lepidolite is a phyllosilicate mineral of the mica group like quartz. It has been used as a source for the extraction of lithium. Lithium gives Lepidolite its dramatic colouration. It is one of the major sources of rare alkali metals: rubidium and caesium. Lepidolite can range in hardness but due to tis particular mineral composition, it is very difficult to carve.
This elegantly simple stone resembles fine marble. Its faceted crystalline appearance lends the stone a unique sense of depth. It is generally pink or pinkish-white in colour but may also be white, grey or even brown or black depending on whether iron and manganese are present minerals in the crystal,
Dolomite lustre is pearly to vitreous to dull. The crystals are translucent to transparent. Dolomites crystal habits include saddle shaped rhombohedral twins and simple rhombs some with slightly curved faces, also prismatic, massive, granular and rock forming.The stone is slightly harder and more resistant to weathering than limestone or marble. It is sedimentary in nature and composed largely of calcium, magnesium and carbonate. Deposits of Dolomite can be found throughout Zimbabwe. Dolomite has a hardness between 3.5 and 4 on the Mohs Hardness Scale.
This uniquely beautiful semi-precious emerald green stone is one of the oldest exposed rocks on the surface of the earth. It was used by the tribesmen in Southern Africa for jewellery and carvings. Witch doctors would also use it to make preparations from the powdered stone which is believed to increase fertility. It is made up mostly of darker shades of green, with striations highlighting changing patterns within the rock of colours ranging from golden browns to rich emerald greens and blues. Found only in South Africa and Zimbabwe, Verdite is a relatively soft stone. Zimbabwean Verdite, however, is unique in containing inclusions of ruby corundum, the second hardest mineral on earth next to diamond - between 7.0 and 9.0 on the Mohs Hardness Scale. The ruby corundum also gives the stone its semi-precious status, corundum being part of the makeup of ruby and sapphire. Ruby Verdite, or Green Gold as it is often referred to as, was declared a semi-precious stone by the British Geological Society around 1985. Only very experienced sculptors are able to work with the difficulties of carving in this hard and variegated medium to bring out its amazing beauty. The value of works by experienced carvers in this rare stone will grow, as it continues to become more difficult to find.