Click here to see photographs from the article on adding minerals to woodturnings (More Woodturning, 2006)
Minerals
I use several factors to determine which minerals get inlaid and when. In many cases I use minerals to fill natural voids in the wood (checks - drying cracks), indentations in bark, or areas that may have rotted away. In other cases I choose to create special grooves to fill with one or more minerals. I try to use the mineral that best complements the color of the wood itself. Malachite, azurite, coral, and rhodochrosite, which are carbonates, are relatively soft and are less likely to damage my turning tools. Therefore they can be inlaid relatively early in the turning process. Lapis and turquoise are so hard that they can't be turned - they can only be shaped by sanding, after the actual turning is finished.
The minerals embedded in my pieces include:


Malachite, Cu2(CO3)(OH)2 is a green ore of copper. It is related to:
Azurite, Cu3(CO2)2(OH)2 which is deep blue, is also an ore of copper. Azurite was used by some of the Old Masters as a blue pigment for oil paintings.
Lapis (Lapis lazuli) is a blue semi-precious form of the mineral Lazurite (Sodalite mineral group). Its formula varies and is quite complex; but basically it is a sodium-calcium silicate with varying amounts of sulfur, sulfate, chlorine, and water (hydroxyl).
Turquoise, CuAl6(PO4)4(OH)8.4H2O is a well known blue-green semiprecious stone.
Chrysocolla, Cu4H4Si4O10(OH)8 is also blue-green, but has less blue than turquoise.
Coral, Mainly CaCO3 is reddish pink. It is illegal to harvest live red coral (a conser- vation measure that I strongly endorse). My coral comes from Bali, where a deposit of fossil (long dead) coral has been found.
Rhodochrosite, MnCO3 is pink.
Abalone Shell (CaCO3) Is simply crushed pieces of the shell of the abalone mollusk. It has a "mother-of-pearl" iridescence.
Pipestone Is not a mineral but rather a very fine-grained hematite-cemented siltstone.
Natural- and Shaped-Edge Pieces
Sometimes I turn pieces that still retain the bark - or, when the bark has come loose and flies off, the shape of the wood just under the bark. These are referred to as "natural-edge" and "shaped-edge" objects. Some folks like them for their rustic appearance and irregular outlines. In virtually all cases they are much more challenging to make, as the lathe tools are "cutting air" for a portion of each revolution of the lathe. They take more time, and the failure rate is higher. Thus for an object of a given size, natural-edge and shaped-edge pieces are more expensive.

A recent addition to the collection is double-natural-edge bowls, where the original wood edge is retained on both the top and bottom! The editor of "Woodturning Design" magazine says that he has never seen this style before; evidently it is unique to The Well Turned Bowl. I have described the process of making double-natural-edge bowls in the newsletter More Woodturning (Vol. 11, #5, p. 11-15, June, 2006)


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