Cochise College           Student Papers in Geology

Geology Home Page                   physical geology  historical geology  planetary  gems           

Roger Weller, geology instructor

wellerr@cochise.edu

Cubic Zirconia
by Katie DeLosReyes
Physical Geology
Fall 2011
    
  

How Cubic Zirconia Is Created
 

 

            Cubic Zirconia has been the largest competitor to the diamond ever since it’s mass production began in 1976. Cubic Zirconia (CZ) is extremely rare in its natural form, this may be surprising until we understand that virtually all cubic zirconia used to make jewelry is man made. However, CZ was not initially made for jewelry, Russians were searching for a substitute to the ruby, which they could use in lasers making laser production cheaper.  

 

 

Figure  SEQ Figure \* ARABIC 1

 

            Cubic Zirconia is the perfect substitute for diamonds because like diamonds it is cubic in its crystal formation. (see figure 1)  In order to make an imitation, a cubic formation must be used or the end result will not be similar in appearance to the diamond. The problem in the past had been that nothing was able to heat zirconium oxide because the temperature required was so high nothing was able to contain it at such a high heat. That all changed with a major invention we all know and use today, the microwave.

 

            A microwave heats from the inside out; it is this technology that allows us to heat zirconium oxide and then cool it at controlled temperatures that cause the material to form it’s own “crucible”. This method of growing crystals is known as the “skull melt”. When calcium or yttrium is added to cubic zirconia then heated, crystals are forced to grow. Below is an illustration on the container that is used when heating zirconium oxide:

 

 

Figure  SEQ Figure \* ARABIC 2

 

There are five steps that take place in order for the crystal to begin to form:

 

STEP 1

            A powdered form of zirconium oxide with calcium or yttrium is heated in a microwave

 

STEP 2

            The interior is heated while the outer edges remain cool, creating a crust

 

STEP 3

            The interior because extremely hot forcing the powdered substance into a liquid, the outer crust then becomes the “skull”

 

STEP 4

            Crystals begin to form as the skull melts, during this the calcium or yttrium used maintains its structure.

 

STEP 5

            When cooling is complete there is a cubic zirconia crystal within an outer skull or zirconium oxide.

           

 

After the skull method of heating has been completed the main crystal must be cut and faceted, here is a look before the cuts:

 

 

Figure  SEQ Figure \* ARABIC 3

 

 

From the stone that is produced there are a variety of shapes, cuts, and colors that can then be made.

 

Chemical additive (in addition to small amounts Ca or Yt)

Color produced

None

Clear

Cerium oxides - CeO2, Ce2O3

Red, orange, and yellow

Copper - CuO, Iron - Fe2O3, Nickel - NiO, Praesiodymium - Pr2O3, and Titanium - TiO2

Yellow, amber, brown

Erbium - Er2O3, Europium - Eu2O3, Holmium - Ho2O3

Pink

Chromium - Cr2O3, Thulium - Tm2O3, Vanadium - V2O3

Olive Green

Cobalt - Co2O3, Manganese - MnO2, Neodymium - Nd2O3

Lilac, violet

Larger quantities of stabilizer

Sapphire blue, emerald.

 

 

            Cubic Zirconia has become popular because it can be cut and colored many different ways to make a variety of jewelry. High quality cubic zirconia can even be difficult for a jeweler to decipher with the naked eye. Since it’s debut in 1978 cubic zirconia has become more and more popular, with about a 10% growth rate and acceptance as the diamond substitute it shows no signs of slowing down. Although there has been a new diamond substitute introduced called synthetic moissanite the process is more expensive than the skull melt technique, making it less cost effective. Cubic Zirconia will surely continue to show up across jewelry stores for some time to come, especially as it is becoming more and more socially accepted.

 

 

Figure  SEQ Figure \* ARABIC 4

 

Figure  SEQ Figure \* ARABIC 5

     

 

                                                Works Cited

 

 

http://www.madehow.com/Volume-5/Cubic-Zirconia.html

 

http://en.wikipedia.org/wiki/Cubic_zirconia

 

http://www.geologyrocks.co.uk/tutorials/cubic_zirconia

 

http://www.yourgemologist.com/CubicZirconia/cubiczirconia.html

 

http://www.diamonds-are-forever.org.uk/cubic-zirconia.htm

 

http://skywalker.cochise.edu/wellerr/mingem/gemsyn/mixed2.htm