WO2007106438A2

WO2007106438A2 - Methods of manufacturing highly polished gemstones

Info

Publication number: WO2007106438A2
Application number: PCT/US2007/006217
Authority: WO
Inventors: Cynthia A. Kuper
Original assignee: Versilant Nanotechnologies Llc
Priority date: 2006-03-10
Filing date: 2007-03-12
Publication date: 2007-09-20
Also published as: WO2007106438A3

Abstract

The invention encompasses the creation of upgraded gemological mineral particles and methods of manufacture and application of such gemological mineral particles. In particular, the invention encompasses a process for grinding gemological minerals into particles and polishing those particles to generate novel high quality gemstones. The application for the polished gem stone particles will be used to make jewelry.

Description

METHODS OF MANUFACTURING HIGHLY POLISHED GEMSTONES

1. FIELD OF THE INVENTION

[0001] The invention encompasses the creation of upgraded gemological mineral particles and methods of manufacture and application of such gemological mineral particles. In particular, the invention encompasses a process for grinding gemological minerals into particles and polishing those particles to generate novel high quality gemstones. The application for the polished gem stone particles will be used to make jewelry.

2. BACKGROUND OF THE INVENTION

[0002] There are a limited number of elements and chemical compounds that have the physical characteristics to be useful as gemstones. The physical characteristics that are generally accepted as being most important are hardness, refractive index and color, although thermal stability, chemical stability and toughness are also considered important in many gemstone applications.

[0003] To date, the only chemical substances technically considered precious stones are diamonds (z.e., single crystalline carbon) and corundum (i.e., sapphire and niby [single crystalline aluminum oxide]) because their hardness when measured on the Mohs scale is approximately 9 or higher. The Mohs system is a scale for ranking hardness of a mineral with diamond being the hardest at 10, sapphire at 9, topaz , 8, down to the softest mineral, talc, which is 1. Emerald, because it is rare, is accepted as a precious stone even though its hardness is 7.5, while other gems, such as chrysoberyl, topaz and garnet, are usually classified as semiprecious stones because of their lower hardness. Hardness has practical value in that it defines the ability of a gemstone to resist scratching.

[0004] Refractive index is important because it defines the ability of a gemstone to refract light. When materials with a high refractive index are fashioned into finished gemstones they sparkle and appear brilliant when exposed to light. The characteristic sparkle of a diamond is due mainly to its high refractive index. [0005J The color of a gemstone is determined by a variety of factors, from the impurity atoms that are available to be incorporated into the crystal lattice to the physical and electronic structure of the crystal itself. A ruby, for instance, is simply a sapphire single crystal (aluminum oxide) that contains a small concentration of chromium impurity atoms.

[0006] The thermal and chemical stability of a gemstone can be important during the process of mounting stones into jewelry. In general, it is beneficial if stones can be heated to high temperatures without changing color or reacting with ambient gases (that mar the surface finish).

[0007] The toughness of a gemstone relates to the ability of the gemstone to absorb energy . without breaking, chipping or cracking. A gemstone must be able to withstand those impact forces normally encountered during a lifetime of use mounted on a ring or other jewelry item.

[0008] Hardness, refractive index, color, thermal/chemical stability and toughness are all characteristics that, in combination, determine the usefulness of a material as a gemstone.

[0009] Dating from the 1960's, an effort to produce gem-quality synthetic diamonds was pursued by General Electric Company as evidenced by numerous patents, including U.S. Pat. No. 4,042,673. These efforts centered around the use of very high pressure/high temperature environments for growth of monocrystalline diamonds on seed crystals. Gem-quality synthetic diamonds generally have not gained commercial acceptance.

[0010] As described in U.S. Pat. No. 5,762,896, it has been discovered that relatively low impurity, translucent, single crystal silicon carbide may be grown with a desired color and thereafter fashioned by faceting and polishing into synthetic gemstones. These gemstones have extraordinary hardness, toughness, chemical and thermal stability, and a high refractive index and dispersion that produce unparalleled brilliance. The single crystals from which the gemstones are produced have been grown by sublimation according to techniques of the type described in U.S. Pat. No. Re. 34,061. 3. SUMMARY OF THE INVENTION

[0011] The invention encompasses a method of manufacturing a highly polished gemstone from a poor quality macroscopic gemstone comprising:

10012] minimizing the poor quality gemstone into smaller gemstone particles;

[0013] polishing the smaller gemstone particles to form a highly polished gemstones.

[0014] Another embodiment encompasses a method of manufacturing a highly polished gemstone from a macroscopic gemstone comprising:

[0015] minimizing macroscopic gemstone into smaller gemstone particles; and

[0016] polishing the smaller gemstone particles to form a highly polished gemstones, wherein said polishing is achieved by chemical mechanical planarization.

4. DETAILED DESCRIPTION OF THE INVENTION

4.1. General Description

[0017] The invention encompasses a method of manufacturing a highly polished gemstone from a poor quality macroscopic gemstone comprising:

[0018] minimizing the poor quality gemstone into smaller gemstone particles;

[0019] polishing the smaller gemstone particles to form a highly polished gemstones.

[0020] In one embodiment, the poor quality gemstone is diamond.

[0021] In one embodiment, the poor quality gemstone is ruby.

[0022] In one embodiment, the poor quality gemstone is sapphire. [0023] In one embodiment, the poor quality gemstone is emerald.

[0024] In one embodiment, the minimizing is done by grinding.

[0025] In one embodiment, the minimizing is done by sanding.

[0026] In one embodiment, the minimizing is done by lapping.

[0027] In one embodiment, the minimizing is done by milling.

[0028] In one embodiment, the polishing is done by chemical mechanical planarization.

[0029] In one embodiment, the polishing is done by nanomaterial polishing.

[0030] Another embodiment encompasses a method of manufacturing a highly polished gemstone from a macroscopic gemstone comprising:

[0031] minimizing macroscopic gemstone into smaller gemstone particles; and

[0032] polishing the smaller gemstone particles to form a highly polished gemstones, wherein said polishing is achieved by chemical mechanical planarization.

[0033] Li one embodiment, the poor quality gemstone is diamond.

[0034] In one embodiment, the poor quality gemstone is ruby.

[0035] In one embodiment, the poor quality gemstone is sapphire.

[0036] In one embodiment, the poor quality gemstone is emerald.

4.2 Cutting Techniques of the Invention

[0037] The invention encompasses various techniques for cutting a gemstone. As used herein, "cutting" refers to taking a larger gemstone, preferably one containing impurities and reducing its size. These techniques encompassed by the invention for cutting a gemstone include, but are not limited to, sawing, grinding, sanding, lapping, drilling, tumbling, faceting or combinations thereof.

4.2.1- Grinding

[0038] In one embodiment, the invention encompasses grinding of macroscopic gemstones, preferably with silicon carbide wheels or diamond-impregnated wheels, is used to shape gemstones to a desired rough form, called a preform. As with sawing, a coolant/lubricant (water or oil) is used to remove debris and prevent overheating. Very coarse diamond or silicon carbide, such as 60 grit, or mesh, (400 micron particles) or 100 grit (150 micron particles) is used for rapid removal of stone, and finer abrasive (600 grit - 30 micron, or 1200 grit - 15 micron) is used for final shaping and sanding.

4.2.2. Sawing

[0039] . In another embodiment, the invention encompasses sawing of macroscopic gemstones, Macropscopic gemstone material that has not been extensively cut and polished is referred to generally as rough. Rough material that has been lightly hammered to knock off brittle, fractured material is said to have been cobbed.

[0040] In a preferred embodiment, macropscopic gemstone sawing of the invention encompasse a thin circular blade usually composed of steel, copper, or a phosphor bronze alloy impregnated along the outer edge with diamond grit and rotating at several thousand surface feet per minute literally scratches its way through a gemstone. A liquid such as oil or water is used to wash away cutting debris and keep the stone and the saw blade from overheating, which could cause damage to both the stone and the sawblade.

[0041] Several sizes of circular rock saws are frequently used by most gemcutters: (1) A slab saw, typically 16 to 24 inches in diameter, is used to cut stones of several inches thickness into relatively thin slabs—often 1/8 to 3/8 inch thick; (2) A trim saw, typically 6 to 10 inches in diameter, is used to cut smaller stones into thin slabs or to cut small sections out of slabs; and (3) A faceter's trim saw, typically 4 inches in diameter, is used with a very thin blade, to saw small pieces of expensive rough.

[0042] There are also jigsaws that employ either a reciprocating wire or a continuous thin metal band. These are useful for cutting curved lines that are impossible with circular saws. They are also useful in minimizing waste on extremely valuable rough material. All gems are cut and polished by progressive abrasion using finer and finer grits of harder substances.

[0043] Diamond, the hardest naturally occurring substance, has a Mohs hardness of 10 and is used as an abrasive to cut and polish a wide variety of materials, including diamond itself. Silicon carbide, a manmade compound of silicon and carbon with a Mohs hardness of 9.5, is also widely used for cutting softer gemstones. Other compounds, such as cerium oxide, tin oxide, chromium oxide, and aluminum oxide, are frequently used in polishing gemstones.

4.2.3. Sanding

[0044] The invention also encompasses sanding of macroscopic gemstones. Sanding is similar to grinding but uses finer abrasives. The sanding of the invention is to remove deep scratches left by coarser abrasives during grinding. Since it removes material less rapidly, it also allows more delicate control over final shaping of the stone prior to polishing. For stones with rounded surfaces, a flexible surface such as a belt sander is often used to avoid creating flat areas and promote smooth curves.

4.2.4. Lapping

[0045] The invention also encompasses lapping of macroscopic gemstones. Lapping is very similar to grinding and sanding, except that it is performed on one side of a rotating or vibrating flat disk known as a lap, and it is used especially to create flat surfaces on a stone (as in faceting). Laps are often made of cast iron, steel, or a copper-bronze alloy, but other materials can also be used. 4.2.5. Drilling

[0046J When a gemcutter desires a hole in or through a gemstone (e.g., a bead), a small rotating rod or tube with a diamond tip, or a slurry of silicon carbide and coolant, is used to drillthrough the stone. Ultrasonic, or vibrating, drills are also very effective, but they tend to be costly and thus reserved for high-volume commercial drilling.

[0047] The drilling of macroscopic gemstone encompassed by the invention includes, but is not limited to, a means by which a rotary method involving abrasive cutting action utilizing a fine grit or very hard (diamond) drill point. In both cases liquid is used to flush particles and to introduce grit into the cutting zone and to remove cuttings. For example, macroscopic gemstones are to be drilled with small holes for the passage of threads and/or filaments so as to be strung or fastened, and it has been a tedius task to apply drills in a manner to introduce and remove grit and/or liquid to and from the cutting zone. The present invention encompasses drilling of gemstones and the like by means which establishes the flow of cutting grit and/or liquid into the cutting zone intermediate the drill tip and the work piece being drilled.

[0048] The invention further encompasses a drill assembly the rides by its own weight upon the cutting zone of the gemstone, with vibratory excursions that are vertical and in line with respect to the drilling axis. Therefore, invention encompasses a mounting means for the vertical excursion of a macroscopic gemstone into and out of engagement with a rotating drill, and preferably by means of an electrically powered vibrator that oscillates the said mounting means.

[0049] The invention also encompasses a magnetic mounting conducive to the versatile application of macroscopic gemstone securement and for the containment of a liquid wash and/or carrier for the grit utilized in the drilling process, for example an abrasive powder having a grain size of 220 per inch (linear). Accordingly, the aforesaid vibrator is capable of excursions that lift the drill and assembly to clear said grit particles and for circulation thereof throughout the cutting zone. Thus, there is a combined floating drill and dynamic gemstone support which characterizes this invention. [0050] The invention further encompasses a drill assembly adapted to be depressed by gravity into engagement with a workpiece, and manually operable to be lifted out of periodic engagement riding upon the cutting zone as governed by the aforesaid vibrator. With the present invention there is a sliding chuck that is adapted to be lifted on a drive stem that is revolved by motor means. A lift ring is provided for manual retraction while gravity normally feeds the chuck and a drill carried thereby into depressed engagement at the cutting zone.

4.2.6. Tumbling

[0051] The invention also encompasses tumbling of macroscopic gemstones. An illustrative embodiment of the invention encompasses a rotary rock tumbler, which roll the macroscopic gemstones over and over, the sharp edges are worn away, until a smooth surface is left

[0052] The tumbler of the invention includes but is not limited to use silicon carbide grit, which is much harder than sand, and therefore much faster than nature's process. When tumbling, the first step is to start out with a coarse grit, move to a fine grit, then proceed to a silicon sand step. Finally, a polishing stage. A common polish is titanium dioxide, which is the same polish used in your toothpaste.

[0053] In an illustrative embodiment, the macroscopic gemstone, the coarse grit, and water are added to the tumbler barrel. With the lid replaced, the barrel is allowed to turn on the base. The rate at which the barrel turns is proportional to the size of the barrel. The macroscopic gemstones tumbler of the invention will preferably turn very slowly to allow the macroscopic gemstones to "climb" the inside wall of the barrel. As the macroscopic gemstones reaches the top of the wall, it rumbles down the other rocks and into the slurry or mixture created by the grit and water. The next time around, the macroscopic gemstones will carry the slurry mixture with it onto other macroscopic gemstones. Using a variety of macroscopic gemstones sizes will improve the final result. Small macroscopic gemstones have a better chance of reaching odd shaped places in larger macroscopic gemstones. If too much water has been added, the slurry will be too thin and the macroscopic gemstones will "float" rather than cascade down. If the barrel is too full, the macroscopic gemstones don't have room to cascade down. If the barrel is not full enough, the macroscopic gemstones won't "climb" the wall.

[0054] In summary, step one rounds the macroscopic gemstone, step two takes the deep scratches out of the macroscopic gemstones; step three removes more fine scratches and prepares smaller gemstone for polishing

4.2.7. Faceting

[0055] The invention also encompassed faceting of gemstones. The faceting of the invention can be applied to transparent gemstones to maximize reflection and refraction, and therefore the gemstone's brilliance, scintillation, and fire. If the gem is correctly cut, then light that passes into the gem will strike the back facets, be reflected twice, and then return to the eye, that is if it hits at an angle that is greater than the critical angle. If the gem is not cut properly, the light entering the gem will be refracted out the bottom of the gem, or it "leaks" out from the stone, i.e. when light lands within the critical angle. The larger the gem's refractive index the smaller the critical angle; the smaller the critical angle, the shallower the stone can be fashioned and still maintain brillancy

[0056] The faceted gemstones consist of three main parts, the crown, girdle, and pavilion. The crown is made up of a table (large facet at the top of the stone), upper main facets ( kite shaped), star facets ( triangular), and upper girdle facets (triangular). The girdle (also known as the setting edge) is the section between the top and bottom of the stone and defines the perimeter, thus the overall shape of the gem. The pavilion has lower girdle facets (16, triangular), lower main facets (8, kite shaped), and the culet (small facet where the pavilion facets meet at a point). The eight lower main facets actually create an octagon shape to the culet.

[0057] The invention includes but is not limited to two basic faceted cuts, the brilliant and step. The emerald cut and round brilliant are the basis from which most other cuts are based. A mixed cut would consist of, for example, a brilliant cut crown and step cut pavilion. Although new cuts are introduced fairly often, in 1988 DeBeers introduced new cuts specifically designed for misshapen or colored diamonds, called the sunflower, dahlia, marigold, zinnia, and fire rose. 4.3. Polishing Techniques of the Invention

[0058] Once the macroscopic gemstone is cut, sawed or ground into the desired shape, it must be sanded to remove rough marks and then it is polished with a variety of agents. Without being limited by theory and depending on the stone hardness and the type of facets, the invention encompasses combining a variety of polishing agents and polishing surfaces to finish the smaller gemstone into brilliant shine.

[0059] In an illustrative embodiment, the invention encompasses using traditional abrasive materials used in the field of nanomaterials to polish the smaller gemstones. Ih another illustrative embodiment, the invention encompasses using chemical mechanical planarization ("CMP"), preferably encompassing nanoparticle oxides. The use of CMP materials may have added effect on the gemological material of extreme polish giving refraction and reflection of light otherwise not seen before.

[0060] During chemical mechanical planarization ("CMP"). after the initial oxide CMP, a second poly CMP process is needed for a substrate contact. The use of CMP twice in the isolation sector in SOI results in an unacceptable polish scratch defect density.

[0061] The invention encompasses chemical mechanical planarization (CMP) of gemstones and, more particularly, to CMP compositions and methods for removing impurity materials from gemstones to provide highly polished gemstones.

[0062] CMP processes of the invention optionally include multiple polishing steps. For example, a "first step" provides an initial surface polish. The first step polishing removes the outermost layer, while leaving a smooth planar surface on the gemstone. After the first step removal, the "second step" polishing can remove additional impurities and ultrapolished sheen to gemstones.

[0063] The multiple polishing steps optionally utilize different slurries or polishing solutions to selectively remove the unwanted portions. In other words, one slurry may be utilized for the "first step" and a second slurry may be utilized for the "second step. [0064] Holland et al. discloses, in U.S. Pat. No. 6,261,158, a multi-step CMP system for polishing metal and barrier materials. Holland attempts to minimize process time by performing the polishing on a single, combined platen. However, the system of Holland utilizes a "first slurry" and a "second slurry" for the removal of the respective materials (i.e., the metal and barrier materials).

[O065] The CMP of the invention can remove topography from the gemstone and provide a extreme polish. The CMP of the invention encompasses a process of smoothing and planing surfaces of gemstones with the combination of chemical and mechanical forces, a hybrid of chemical etching and free abrasive polishing. Mechanical grinding alone causes too much surface damage, while wet etching alone cannot attain good planarization. Most chemical reactions are isotropic and etch different crystal planes with different speed. CMP involves both effects, optionally at the same time.

[0066] A typical CMP tool of the invention comprises a rotating platen, that is covered by a pad. The gemstone is mounted in a carrier on a backing film. The retaining ring keeps the gemstone in the correct horizontal position. Both, the platen and the carrier are rotating. Good speed control is preferable. The carrier is also oscillating. For loading and unloading a robot system is installed.

[0067] During chemical mechanical polishing, pressure is applied by down force on the carrier, transferred to the the carrier through the carrier axis and a gimbal mechanism. Beside that also gas pressure or back pressure is loaded on the gemstone. The fact that high points on the gemstone are subjected to higher pressures compared to lower points, hence, the removal rates there are enhanced and planarization is achieved.

[0068] The slurry is supplied from above on the platen. Process relevant are the grain size and material of the abrasive component and the pH control of the slurry. Normally alkalic conditions are used.

[0069] Thermal management is preferable for the CMP of the invention. The polishing speed depends much on the temperature and during CMP heat is generated by reaction heat and abrasive friction. Therefore the platen has a temperature control system, than can adjust the temperature between 10⁰C and 7O⁰C. This is done either by back spray technology as shown in the graphic or by contact with a water cooled support and transmission ring, vacuum locked to the platen. A typical CMP system also involves a pad conditioning tool as well as a tool for the gemstone cleaning after CMP.

10070] Equivalents are within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art and are intended to fall within the appended claims.

Claims

THE CLAIMSWhat is claimed is:

1. A method of manufacturing a highly polished gemstone from a poor quality gemstone comprising:

minimizing the poor quality gemstone into smaller gemstone particles;

polishing the smaller gemstone particles to form a highly polished gemstones.

2. The method of claim 1, wherein the poor quality gemstone is diamond.

3. The method of claim 1 , wherein the poor quality gemstone is ruby.

4. The method of claim 1, wherein the poor quality gemstone is sapphire.

5. The method of claim 1, wherein the poor quality gemstone is emerald.

6. The method of claim 1, wherein the minimizing is done by grinding.

7. The method of claim 1, wherein the minimizing is done by sanding.

8. The method of claim 1, wherein the minimizing is done by lapping.

9. The method of claim 1, wherein the minimizing is done by milling.

10. The method of claim 1, wherein the polishing is done by chemical mechanical planarization.

11. The method of claim 1, wherein the polishing is done by nanomaterial polishing.

12. A method of manufacturing a highly polished gemstone from a macroscopic gemstone comprising: minimizing macroscopic gemstone into smaller gemstone particles; and

polishing the smaller gemstone particles to form a highly polished gemstones, wherein said polishing is achieved by chemical mechanical planarization.

13. The method of claim 12, wherein the poor quality gemstone is diamond.

14. The method of claim 12, wherein the poor quality gemstone is ruby.

15. The method of claim 12, wherein the poor quality gemstone is sapphire.

16. The method of claim 12, wherein the poor quality gemstone is emerald.