The pearl house Mikimoto has created a proprietary grading system for its South Sea cultured pearls collection similar to its Akoya grading system established in 1974.
Useful links:
www.mikimoto.com
www.mikimotoamerica.com
Thursday, June 14, 2007
DTC Sights For Rough Producers
Chaim Even-Zohar writes about DTC sight application + Mining Competitive Policy + Supplier of Choice assessment process + the DTC policy implications @
http://www.idexonline.com/portal_FullEditorial.asp?TextSearch=&KeyMatch=0&id=27497
http://www.idexonline.com/portal_FullEditorial.asp?TextSearch=&KeyMatch=0&id=27497
The Gilson Opal Triplet And How To Make It
Julius Lippa and Pierre Gilson writes:
The opal triplet is a three piece gemstone made by cementing together a thin piece of precious opal sandwiched between a backing piece and a layer of optical quartz or other hard clear material.
Gilson opal: Gilson 'T'Quality opal is specifically made for triplets. It was created to satisfy the wishes and desires of countless opal lovers for the ideal material.
No matrix: Gilson opal is 100% usable since it is solid opal with no matrix.
Toughness: Gilson opal is tougher, harder and can withstand more heat than most opal. However, as with any fine gem material it deserves to be handled with care.
Material list
Opal: Triplet grade precious opal.
Cap material: Optical quartz, (natural or synthetic), sapphire or hard optical glass.
Base material: Jade, opal potch, agate, jasper, basenite, obsidian, glass or plastic.
Epoxy: Two part epoxy which dries water clear.
Lampblack: Lampblack for backing if needed or desired.
Lapidary equipment: Equipment necessary to make flat surfaces and to finish a cabochon.
Steps to follow
1. Color: Wet opal with clean water to show color pattern.
2. Orient: Orient opal for best color pattern for sawing.
3. Sawing: Use thin saw blade to avoid wasting opal in saw cut. Use a saw vise or a steady rest rather than trying to do this freehand (see # 7 opal thickness)
4. Grinding: Assuming that your saw blade leaves smooth areas on the sawed materials start with # 220 abrasive, then go to # 600 abrasive. It usually is not necessary to go beyond # 600. The perfectionist who continues to finer finishes such as # 1200 or finer (a semi-polish) will then have the brightest triplets.
5. Method: The individual method of grinding flat surfaces depends upon available equipment, personal preferences or techniques such as:
a) Abrasives of various sizes used on a sheet of flat glass. (use entire surface area so low spots do not develop)
b) Wet or dry abrasive paper used on flat surface.
c) Faceting laps. (highly recommended and used by Gilson Labs)
d) Flat-faced diamond discs. (highly recommended and used by Gilson Labs)
6. Cleanliness: Wash hands and material being worked on after each step to avoid contamination.
7. Opal thickness: How thin to grind the opal depends upon personal preference in color. Usually the thinner the opal the darker the color. As a starting point begin at 0.20mm (.008 inch) slices and if you feel it is necessary work the opal thinner until color suits you. (See # 16)
8. Base thickness: Base thickness 1/16 inch (1.6mm) or as desired to fit mounting. Put a 30 to 45 degree angle on base to clear mounting.
9. Cap thickness: Cap thickness can vary from 1/16th inch to ¼ inch (1.6 to 6mm). This is an area where the size of the triplet and personal tastes dictate the answer. The thicker the cap the more the magnification effect, but also the heavier the triplet becomes.
10. Components: The base and cap materials receive similar treatment as the opal to get to a finished surface. The exception would be when caps in their finished state are cemented to the opal and are not formed from an original piece of rough material.
11. Cleanliness: Before cementing any triplet components together we come to a very important subject; Cleanliness which is the secret of a good bond. Clean all surfaces which are glued together with acetone. Let dry, then clean with alcohol.
12. Cleaners: Cleaners cementing leave residue, therefore freshly ground surfaces after step 11 above can be rinsed with clean water and allowed to dry on clean paper or rags without ever again touching the ground surfaces with your fingers or anything else prior to joining together.
13. Heat: Dry opal, cap and base materials at temperatures under 180 degrees Fahrenheit (82 degrees centigrade) in oven, or on top of oven near pilot light or under an electric light bulb. Bring up to drying temperatures gradually ( see # 20)
14. Three parts: When all three parts of the triplet (flat surfaces) have been prepared they then are joined together, two pieces at a time, with a two part epoxy which dries water clear. (see # 19 for use of lampblack)
15. Handling: For ease in handling after one surface of the opal has been finished glue finished surface to backing or cap to grind opal thin enough to get best color (see # 19 for use of lampblack)
16. Checking for color: Wet the opal cemented to cap and place on a shiny black surface such as a piece of glazed tile to judge when color is clear and bright. If color does not suit your tastes, grind thinner until it meets with your approval, alternating between grinding and checking until you are satisfied. Repeat same method of checking and grinding for opal mounted on backing.
17. Assembly: Mix epoxy gently to avoid air bubbles and apply epoxy in thin layer to both surfaces which you join together. These two components should be warm when put together. Put the two pieces together with firm finger pressure and a sliding motion to squeeze out air bubbles and surplus epoxy. Use little clamps, clothes pins, weights, etc. to hold parts together until epoxy sets properly (24 hours).
18. Surfaces: All surfaces which are joined together must be flat, clean, dry and scratch free. Any uneven area between surfaces may capture air and be visible as air bubbles or opaque spots.
19. Lampblack: The use of lampblack in the epoxy gives a bright black shiny surface to the backing material and also permits the use of base materials which are not black originally. The amount of lampblack to use in epoxy is about .5mm in diameter for a 10 x 12 mm stone. It is a trial and error method easily learned after a few trials on test materials.
Note: Using too much lampblack degrades the epoxy resulting in a weak bond and using too little lampblack results in epoxy not being dark enough. Most black materials become sufficiently reflective with use of clear epoxy and addition of lampblack is not needed.
20. Water: Use plenty of water when working with the opal to keep it cool. Do not lean the hard way that overheated opal may crack or craze.
21. Clarity: Everything possible should be done for utmost clarity and a part of this process is to use an epoxy which dries water clear. Any coloring in the epoxy between the cap and the opal will dull the color of the opal.
22. Cap: The cap used over the opal must be flawless and water clear since this domed crystal cover both magnifies and enhances the colors and patterns while at the same time protecting the opal.
23. Color change: Experimentation with various base materials revealed that the red and pink colors in an occasional piece of opal from any source would be greatly improved when backed with a bright red material. In opal which exhibits this phenomena the red and pink colors are already visible. These make up into very pleasant stones when backed with black, however, some people think the red backing produces a great improvement.
24. Base: Almost any strong material can be used which expands and contracts at approximately the same rate as opal. (avoid brittle materials)
25. Durability: Opal like glass is six on the Moh’s scale of hardness. Cementing a quartz cover on top of the opal increases the hardness to seven plus or to nine with a clear sapphire cover.
26. Free forms: Free form triplets with their unique charm are especially adaptable to modern jewelry, lending themselves to great variety of design.
27. Good food: You well may ask how <> gets into an instruction sheet on triplets. It was inserted to remind you that like good food the triplets you make can only be as good as the ingredients used and the skill and craftsmanship of the worker.
28. Black opal: The opal triplet probably was created by an unknown genius to save and use thin bands of precious opal. He little realized that his brain child often leads to confusion between genuine black opal and very good triplets even amongst those in the jewelry trade. This sort of confusion can occur when a thin cap is used and the juncture of cap to opal can not be seen when hidden in a mounting.
29. Magnifying lens: A magnifying lens is a handy item to use when assembling triplets so you can look for air bubbles and if any are objectionable to you then slide the parts apart and wash off with alcohol, dry and try again.
30. Other opal: Precious opal suitable as triplet material from any of the world’s sources may also be processed with these instructions.
31. Lapidary: It is assumed that the reader has mastered the techniques of lapidary. Finishing the triplet is simply the process of making a cabochon.
These are some mistakes people have made and things to avoid:
- Opal slices used so thick that black backing has no effect.
- Despite emphasis on using clear cap examples of window glass with all kinds of inclusions, bubbles, etc., as well as quartz with flaws and yellow discoloration have been used with poor results.
- Opal used in wedge shape so one end of triplet is dull and the other end bright.
- Epoxy mixed on a dirty surface resulting in triplet with a weak bond or visible dirt within.
- Using very old epoxy with the catalyst spoiled so the epoxy will not harden properly.
The opal triplet is a three piece gemstone made by cementing together a thin piece of precious opal sandwiched between a backing piece and a layer of optical quartz or other hard clear material.
Gilson opal: Gilson 'T'
No matrix: Gilson opal is 100% usable since it is solid opal with no matrix.
Toughness: Gilson opal is tougher, harder and can withstand more heat than most opal. However, as with any fine gem material it deserves to be handled with care.
Material list
Opal: Triplet grade precious opal.
Cap material: Optical quartz, (natural or synthetic), sapphire or hard optical glass.
Base material: Jade, opal potch, agate, jasper, basenite, obsidian, glass or plastic.
Epoxy: Two part epoxy which dries water clear.
Lampblack: Lampblack for backing if needed or desired.
Lapidary equipment: Equipment necessary to make flat surfaces and to finish a cabochon.
Steps to follow
1. Color: Wet opal with clean water to show color pattern.
2. Orient: Orient opal for best color pattern for sawing.
3. Sawing: Use thin saw blade to avoid wasting opal in saw cut. Use a saw vise or a steady rest rather than trying to do this freehand (see # 7 opal thickness)
4. Grinding: Assuming that your saw blade leaves smooth areas on the sawed materials start with # 220 abrasive, then go to # 600 abrasive. It usually is not necessary to go beyond # 600. The perfectionist who continues to finer finishes such as # 1200 or finer (a semi-polish) will then have the brightest triplets.
5. Method: The individual method of grinding flat surfaces depends upon available equipment, personal preferences or techniques such as:
a) Abrasives of various sizes used on a sheet of flat glass. (use entire surface area so low spots do not develop)
b) Wet or dry abrasive paper used on flat surface.
c) Faceting laps. (highly recommended and used by Gilson Labs)
d) Flat-faced diamond discs. (highly recommended and used by Gilson Labs)
6. Cleanliness: Wash hands and material being worked on after each step to avoid contamination.
7. Opal thickness: How thin to grind the opal depends upon personal preference in color. Usually the thinner the opal the darker the color. As a starting point begin at 0.20mm (.008 inch) slices and if you feel it is necessary work the opal thinner until color suits you. (See # 16)
8. Base thickness: Base thickness 1/16 inch (1.6mm) or as desired to fit mounting. Put a 30 to 45 degree angle on base to clear mounting.
9. Cap thickness: Cap thickness can vary from 1/16th inch to ¼ inch (1.6 to 6mm). This is an area where the size of the triplet and personal tastes dictate the answer. The thicker the cap the more the magnification effect, but also the heavier the triplet becomes.
10. Components: The base and cap materials receive similar treatment as the opal to get to a finished surface. The exception would be when caps in their finished state are cemented to the opal and are not formed from an original piece of rough material.
11. Cleanliness: Before cementing any triplet components together we come to a very important subject; Cleanliness which is the secret of a good bond. Clean all surfaces which are glued together with acetone. Let dry, then clean with alcohol.
12. Cleaners: Cleaners cementing leave residue, therefore freshly ground surfaces after step 11 above can be rinsed with clean water and allowed to dry on clean paper or rags without ever again touching the ground surfaces with your fingers or anything else prior to joining together.
13. Heat: Dry opal, cap and base materials at temperatures under 180 degrees Fahrenheit (82 degrees centigrade) in oven, or on top of oven near pilot light or under an electric light bulb. Bring up to drying temperatures gradually ( see # 20)
14. Three parts: When all three parts of the triplet (flat surfaces) have been prepared they then are joined together, two pieces at a time, with a two part epoxy which dries water clear. (see # 19 for use of lampblack)
15. Handling: For ease in handling after one surface of the opal has been finished glue finished surface to backing or cap to grind opal thin enough to get best color (see # 19 for use of lampblack)
16. Checking for color: Wet the opal cemented to cap and place on a shiny black surface such as a piece of glazed tile to judge when color is clear and bright. If color does not suit your tastes, grind thinner until it meets with your approval, alternating between grinding and checking until you are satisfied. Repeat same method of checking and grinding for opal mounted on backing.
17. Assembly: Mix epoxy gently to avoid air bubbles and apply epoxy in thin layer to both surfaces which you join together. These two components should be warm when put together. Put the two pieces together with firm finger pressure and a sliding motion to squeeze out air bubbles and surplus epoxy. Use little clamps, clothes pins, weights, etc. to hold parts together until epoxy sets properly (24 hours).
18. Surfaces: All surfaces which are joined together must be flat, clean, dry and scratch free. Any uneven area between surfaces may capture air and be visible as air bubbles or opaque spots.
19. Lampblack: The use of lampblack in the epoxy gives a bright black shiny surface to the backing material and also permits the use of base materials which are not black originally. The amount of lampblack to use in epoxy is about .5mm in diameter for a 10 x 12 mm stone. It is a trial and error method easily learned after a few trials on test materials.
Note: Using too much lampblack degrades the epoxy resulting in a weak bond and using too little lampblack results in epoxy not being dark enough. Most black materials become sufficiently reflective with use of clear epoxy and addition of lampblack is not needed.
20. Water: Use plenty of water when working with the opal to keep it cool. Do not lean the hard way that overheated opal may crack or craze.
21. Clarity: Everything possible should be done for utmost clarity and a part of this process is to use an epoxy which dries water clear. Any coloring in the epoxy between the cap and the opal will dull the color of the opal.
22. Cap: The cap used over the opal must be flawless and water clear since this domed crystal cover both magnifies and enhances the colors and patterns while at the same time protecting the opal.
23. Color change: Experimentation with various base materials revealed that the red and pink colors in an occasional piece of opal from any source would be greatly improved when backed with a bright red material. In opal which exhibits this phenomena the red and pink colors are already visible. These make up into very pleasant stones when backed with black, however, some people think the red backing produces a great improvement.
24. Base: Almost any strong material can be used which expands and contracts at approximately the same rate as opal. (avoid brittle materials)
25. Durability: Opal like glass is six on the Moh’s scale of hardness. Cementing a quartz cover on top of the opal increases the hardness to seven plus or to nine with a clear sapphire cover.
26. Free forms: Free form triplets with their unique charm are especially adaptable to modern jewelry, lending themselves to great variety of design.
27. Good food: You well may ask how <> gets into an instruction sheet on triplets. It was inserted to remind you that like good food the triplets you make can only be as good as the ingredients used and the skill and craftsmanship of the worker.
28. Black opal: The opal triplet probably was created by an unknown genius to save and use thin bands of precious opal. He little realized that his brain child often leads to confusion between genuine black opal and very good triplets even amongst those in the jewelry trade. This sort of confusion can occur when a thin cap is used and the juncture of cap to opal can not be seen when hidden in a mounting.
29. Magnifying lens: A magnifying lens is a handy item to use when assembling triplets so you can look for air bubbles and if any are objectionable to you then slide the parts apart and wash off with alcohol, dry and try again.
30. Other opal: Precious opal suitable as triplet material from any of the world’s sources may also be processed with these instructions.
31. Lapidary: It is assumed that the reader has mastered the techniques of lapidary. Finishing the triplet is simply the process of making a cabochon.
These are some mistakes people have made and things to avoid:
- Opal slices used so thick that black backing has no effect.
- Despite emphasis on using clear cap examples of window glass with all kinds of inclusions, bubbles, etc., as well as quartz with flaws and yellow discoloration have been used with poor results.
- Opal used in wedge shape so one end of triplet is dull and the other end bright.
- Epoxy mixed on a dirty surface resulting in triplet with a weak bond or visible dirt within.
- Using very old epoxy with the catalyst spoiled so the epoxy will not harden properly.
Jewelry Appraisals
Kathryn Barcham writes:
Jewelry appraisers are often asked to explain the service they offer and why this is necessary. An appraisal service is usually established for the purpose of:
1. Supplying estimates of replacement costs that will suffice for insurance purposes.
2. Estate appraising for tax purposes.
3. Advice on private sales between two or more persons.
4. Personal interest.
A jewelry appraisal may be offered by the jeweler when the item is purchased and is insured for the retail value. Appraisals may also be done by a gemologist or other person familiar with current prices. Appraisal of merchandise purchased elsewhere should not be attempted unless the appraiser has the training and equipment necessary to identify and classify according to quality all the materials and jewelry brought to this attention. Naturally any jeweler can appraise merchandise sold by his firm, since he knows its quality and retail price but appraising jewelry sold by another firm or brought in another country can cause problems since there is a rather wide variation in markup used by different types of firms for smaller merchandise. Their valuations must relay on fair market value which can best be described as the estimated cost of replacing each item through the firms own suppliers as of that date.
Estate appraisals or similar appraisals are usually considered on the basis of immediate or so called distress values i.e value of an article is determined by what it could be sold for immediately. Most appraisers determine this price by considering what they would be willing to pay for the item at that time or what they estimate it would bring at auction.
Accepting jewelry for appraisal
1. Ask the customer to state the reason for appraisal as it may influence the valuation, e.g. estate duty, personal insurance, personal interest etc.
2. Considerable caution should be exercised when accepting jewelry for appraisal particularly when it is to be retained for a considerable length of time. Most people are unfamiliar with the quality of their jewelry and are frequently under the impression that it is more valuable than it actually is. In such instances, if the jewelry is returned with an appraisal that lists the damages or imperfections that the customer was not aware of, the appraiser may be accused of substitution. The piece should also be examined closely under a lens, or preferable with a microscope, and the customer’s attention called to any serious imperfections or blemishes in the stones and any serious damage or wear to mounting. Many people assume that all antique pieces are genuine and are not aware that man-made rubies have been on the market since 1904, synthetic sapphires since 1910, synthetic spinel (primarily imitating aquamarine, sapphire and zircon) since 1920’s and synthetic emeralds have been commercially available since 1950’s. Although synthetic gem quality diamonds of cuttable size, have been manufactured, they are not something to worry about at this time since they cost more to produce synthetically than to mine the best quality natural material. On other hand, the market abounds with diamond simulants probably the best known being cubic zirconium (CZ, Gemeron, Blunco Counterfeit Diamonds, etc). A quick test with a Presidium thermal reaction tester or similar instrument will tell whether the stone is a diamond or a stimulant and prevent any embarrassment to customer and jeweler alike.
3. The customer should be issued with a receipt that lists:
a) A brief description of the piece.
b) The number and measurements of important stones and a general description of their quality. (Actual identity should not be listed unless they have been tested.)
c) A statement to the effect that ‘Acceptance of jewelry for appraisals or repair does not constitute an acknowledgment or confirmation of identity or quality of pieces claimed by the owner.” Often jewelers will photograph the piece and this allows for a more accurate reproduction of the item in the event of loss. Customers are often more satisfied with an appraisal that includes a photograph of their jewelry.
Appraisal form
If the customer, as well as the insurance company, is to be given maximum protection, an appraisal must include a complete description of the merchandise. Many jewelers do not abide by this precaution and continue to issued indefinite appraisals that are worded, e.g “One diamond ring retail value of which $ xxx. Insurance companies rarely reject such an appraisal. Should a claim be made on a lost stone, a much less expensive diamond may be substituted for such an imprecisely described ring. On the other hand, should the piece contain an imitation stone, they are liable for replacement with a genuine stone. Therefore the appraisal must include a complete description of the mounting (type of metal and style) together with exact measurements, imperfections, color grades, proportions and finish classifications of diamonds and other gems. A complete appraisal helps to assure the procurement of an exact duplicate of the item or another one of equal value. The appraisal form may be imprinted with the name of the appraising firm with space for the customers address and the date of appraisal. It should be signed by the appraiser.
Appraisal update
Sending annual reminders regarding cleaning, checking and reappraising can be helpful to the customer. Many tend to forget to check the items for damage to stones, worn prongs and shanks, which are the result of normal wear and tear, and to update their policies against inflation. Sometimes when examining jewelry that has been submitted for the purpose of bringing insurance coverage up to current market prices, incorrect grading or identification of stones have been discovered. The reappraisal should contain the correct identification, grading and valuation of the stones at the current market value; even if the value is less than the original appraisal. After checking the stones carefully, merely state what you believe the items would cost to replace in your store. You may find however that the appraisal value will not require change for several years.
Jewelry appraisers are often asked to explain the service they offer and why this is necessary. An appraisal service is usually established for the purpose of:
1. Supplying estimates of replacement costs that will suffice for insurance purposes.
2. Estate appraising for tax purposes.
3. Advice on private sales between two or more persons.
4. Personal interest.
A jewelry appraisal may be offered by the jeweler when the item is purchased and is insured for the retail value. Appraisals may also be done by a gemologist or other person familiar with current prices. Appraisal of merchandise purchased elsewhere should not be attempted unless the appraiser has the training and equipment necessary to identify and classify according to quality all the materials and jewelry brought to this attention. Naturally any jeweler can appraise merchandise sold by his firm, since he knows its quality and retail price but appraising jewelry sold by another firm or brought in another country can cause problems since there is a rather wide variation in markup used by different types of firms for smaller merchandise. Their valuations must relay on fair market value which can best be described as the estimated cost of replacing each item through the firms own suppliers as of that date.
Estate appraisals or similar appraisals are usually considered on the basis of immediate or so called distress values i.e value of an article is determined by what it could be sold for immediately. Most appraisers determine this price by considering what they would be willing to pay for the item at that time or what they estimate it would bring at auction.
Accepting jewelry for appraisal
1. Ask the customer to state the reason for appraisal as it may influence the valuation, e.g. estate duty, personal insurance, personal interest etc.
2. Considerable caution should be exercised when accepting jewelry for appraisal particularly when it is to be retained for a considerable length of time. Most people are unfamiliar with the quality of their jewelry and are frequently under the impression that it is more valuable than it actually is. In such instances, if the jewelry is returned with an appraisal that lists the damages or imperfections that the customer was not aware of, the appraiser may be accused of substitution. The piece should also be examined closely under a lens, or preferable with a microscope, and the customer’s attention called to any serious imperfections or blemishes in the stones and any serious damage or wear to mounting. Many people assume that all antique pieces are genuine and are not aware that man-made rubies have been on the market since 1904, synthetic sapphires since 1910, synthetic spinel (primarily imitating aquamarine, sapphire and zircon) since 1920’s and synthetic emeralds have been commercially available since 1950’s. Although synthetic gem quality diamonds of cuttable size, have been manufactured, they are not something to worry about at this time since they cost more to produce synthetically than to mine the best quality natural material. On other hand, the market abounds with diamond simulants probably the best known being cubic zirconium (CZ, Gemeron, Blunco Counterfeit Diamonds, etc). A quick test with a Presidium thermal reaction tester or similar instrument will tell whether the stone is a diamond or a stimulant and prevent any embarrassment to customer and jeweler alike.
3. The customer should be issued with a receipt that lists:
a) A brief description of the piece.
b) The number and measurements of important stones and a general description of their quality. (Actual identity should not be listed unless they have been tested.)
c) A statement to the effect that ‘Acceptance of jewelry for appraisals or repair does not constitute an acknowledgment or confirmation of identity or quality of pieces claimed by the owner.” Often jewelers will photograph the piece and this allows for a more accurate reproduction of the item in the event of loss. Customers are often more satisfied with an appraisal that includes a photograph of their jewelry.
Appraisal form
If the customer, as well as the insurance company, is to be given maximum protection, an appraisal must include a complete description of the merchandise. Many jewelers do not abide by this precaution and continue to issued indefinite appraisals that are worded, e.g “One diamond ring retail value of which $ xxx. Insurance companies rarely reject such an appraisal. Should a claim be made on a lost stone, a much less expensive diamond may be substituted for such an imprecisely described ring. On the other hand, should the piece contain an imitation stone, they are liable for replacement with a genuine stone. Therefore the appraisal must include a complete description of the mounting (type of metal and style) together with exact measurements, imperfections, color grades, proportions and finish classifications of diamonds and other gems. A complete appraisal helps to assure the procurement of an exact duplicate of the item or another one of equal value. The appraisal form may be imprinted with the name of the appraising firm with space for the customers address and the date of appraisal. It should be signed by the appraiser.
Appraisal update
Sending annual reminders regarding cleaning, checking and reappraising can be helpful to the customer. Many tend to forget to check the items for damage to stones, worn prongs and shanks, which are the result of normal wear and tear, and to update their policies against inflation. Sometimes when examining jewelry that has been submitted for the purpose of bringing insurance coverage up to current market prices, incorrect grading or identification of stones have been discovered. The reappraisal should contain the correct identification, grading and valuation of the stones at the current market value; even if the value is less than the original appraisal. After checking the stones carefully, merely state what you believe the items would cost to replace in your store. You may find however that the appraisal value will not require change for several years.
Wednesday, June 13, 2007
Actinolite
Crystallography: Monoclinic, bladed crystals, usually elongated; fibrous, columnar aggregates; massive; granular; twinned.
Colors: Light to dark green, blackish green
Luster: Vitreous
Hardness: 5.5
Specific gravity: 3.05 - 3.44
Cleavage: 2 directions, good, often fibrous nature; brittle, compact variety tough.
Refractive index: 1.619 –1.644
Birefringence: 0.022 – 0.026
Pleochroism: yellow to dark green.
Spectrum: faint line at 503nm
Luminescence: none due to presence of iron.
Occurrence: Contact metamorphic limestones and dolomites.
Madagascar: small, dark green crystals.
Tanzania: transparent crystals.
USA
Stone sizes: Actinolite is rarely facetable and usually in small fragments. Material from Chester, Vermont, USA could provide large stones.
Comments: Chatoyant material is cut to exhibit cat’s eye phenomena. Actinolite is a constituent of nephrite jade; easy to cleave and difficult to cut—for this reason it may not be an ideal stone for jewelry. Quartz cat’s eye, Apatite cat’s eye, Chrysoberyl cat’s eye, Cathay stone (man-made glass) may be confused for Actinolite cat’s eye.
Colors: Light to dark green, blackish green
Luster: Vitreous
Hardness: 5.5
Specific gravity: 3.05 - 3.44
Cleavage: 2 directions, good, often fibrous nature; brittle, compact variety tough.
Refractive index: 1.619 –1.644
Birefringence: 0.022 – 0.026
Pleochroism: yellow to dark green.
Spectrum: faint line at 503nm
Luminescence: none due to presence of iron.
Occurrence: Contact metamorphic limestones and dolomites.
Madagascar: small, dark green crystals.
Tanzania: transparent crystals.
USA
Stone sizes: Actinolite is rarely facetable and usually in small fragments. Material from Chester, Vermont, USA could provide large stones.
Comments: Chatoyant material is cut to exhibit cat’s eye phenomena. Actinolite is a constituent of nephrite jade; easy to cleave and difficult to cut—for this reason it may not be an ideal stone for jewelry. Quartz cat’s eye, Apatite cat’s eye, Chrysoberyl cat’s eye, Cathay stone (man-made glass) may be confused for Actinolite cat’s eye.
Minimalist Approach
"Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away."
- Antoine de Saint-Exupery
- Antoine de Saint-Exupery
The Coming Collapse Of The US Dollar
M R Venkatesh writes about global imbalance + orderly devaluation + the massive size of America's twin deficits: trade and budgetary @ http://www.rediff.com/money/2007/jun/11dollar.htm
Who Owns Most Gold?
(via Commodity Online) If we take national gold reserves, then the most gold is owned by the United States, followed by Germany and the International Monetary Fund.
But if we include jewelry ownership, then India is the largest repository of gold in terms of total gold within the national boundaries. In terms of personal ownership, it is not known who owns the most, but it is possibly a member of a ruling royal family in the East.
But if we include jewelry ownership, then India is the largest repository of gold in terms of total gold within the national boundaries. In terms of personal ownership, it is not known who owns the most, but it is possibly a member of a ruling royal family in the East.
Subscribe to:
Comments (Atom)