SHOW: Rings 223

Title:      Ring.
General:    18K Gold Ring, set with Cooper Pedy white Opal.
Material:   18K Gold.
Gem:        White Opal.
Method:     Cast, constructed.
Finish:     Polished.
Mechanics:  Claw set.
Designer:   W.van Heeckeren.
Craftsman:  W.van Heeckeren.

Price:      AUS $ 12000.00.


        18K GOLD is a ternary Gold alloy consisting of:
                        750 parts/1000 Pure Gold.
                        125 parts/1000 Pure Silver.
                        125 parts/1000 Pure Copper.
 Annealing temperature: 750 degrees Celsius.
   Melting Temperature: 950 degrees Celsius.



            CASTING is a method by which moulten metal is poured into a mold
                    in order to achieve the desired shape.  In the "Lost
                    Wax" method, an accurate wax model is made.  The wax
                    model is invested (put in a chrystobalite plaster),
                    after the investment has set, the wax is burned out in
                    a Kiln.  This leaves a negative cavity into which the
                    moulten metal may be poured.



        Claw Setting is done by making a setting from wire, which
                        has a support for the stone, from which emanate
                        wires, which can be bent over the stone to hold it
                        in place.


Technical Data for OPAL.

name:                   OPAL (Quartz group)
colour:                 White, gray, blue, green, orange
colour of streak:       White
mohs hardness:          5.5-6.5
specific gravity:       1.98-2.20
cleavage:               None
fracture:               Conchoidal, splintery, brittle
crystal system:         Amorphous; kidney or grape-shaped aggregates
chemical composition:   SiO2.nH2O hydrous silicon dioxide
transparency:           Transparent, opaque
refractive index:       1.44-1.46
double refraction:      None
dispersion:             None
pleochroism:            None
absorption spectrum:    Fire opal: 7000-6400, 5900-4000
fluorescence:           White:white, bluish, brownish, greenish.
                        Black:usually none Fire:greenish to brown