Rhodium
Rhodium is a chemical element that is a rare, silvery-white, hard transition metal and a member of the platinum group. Rhodium is found in platinum ores and is used in alloys with platinum and as acatalyst. It is abbreviated to Rh and has atomic number 45. It is one of the most expensive precious metals.
Valuable metal prices containg all precious metals names | metal | mass abundance | price 2009-04-10 | price 2009-07-22 |
|---|
| Platinum | 5×10−9 | 42681 $/kg | 37650 $/kg |
| Rhodium | 1×10−9 | 39680 $/kg | 46200 $/kg |
| Gold | 4×10−9 | 31100 $/kg | 30590 $/kg |
Platinum
Platinum is a white metal, but unlike gold it is used in jewelry in almost its pure form (approximately 95% pure).
Platinum is extremely long wearing and is very white, so it does not need to be Rhodium plated like white gold. Its natural color is a gray color.Platinum is very dense (heavy), so a platinum ring will feel heavier than an 18kt gold ring.
Platinum is, however, very expensive. A platinum ring will be approximately twice the price of an 18kt white gold ring (excluding gemstone costs).
The Platinum Group of Metals
Six related metals belong to the Platinum Group of Metals, or PGM:
· Platinum
· Iridium
· Palladium
· Ruthenium
· Rhodium
· Osmium
Platinum Marks Jewelry can contain different percentages of pure platinum. The US Federal Trade Commission, FTC, publishes guidelines for acceptable marking standards for platinum jewelry sold in the US.
Platinum content is usually expressed as the amount of pure platinum the jewelry contains in parts per thousand. Think about it like this... you mix up a huge bucket of fruit tea that contains 1,000 ounces--900 hundred of the ounces are plain tea and 100 are fruit juice. That makes the tea 900 parts per thousand of your mix. Another way to express that is to say that tea makes up ninety percent of the mix--900 divided by 1000.
· Jewelry that contains at least 950 parts per thousand of pure platinum may be marked or described as "Platinum"
· Jewelry that contains 850, 900 or 950 parts per thousand of pure platinum may be marked "Plat" or "Pt" if a number is used in front of the term to disclose the amount of pure platinum in the mix, such as
· "850 Plat" or "850 Pt", or
· "950 Plat" or "950 Pt"
· Jewelry that contains at least 950 parts per thousand of platinum group metals, with at least 500 parts per thousand of the total pure platinum, may be marked as platinum as long as the numbers of each metal are disclosed. For instance,
· "600 Pt. 350 Ir." or 600 Plat. 350 Irid." for 600 parts pure platinum and 350 parts iridium
· "550Pt. 350Pd. 50Ir." or "550Plat. 350Pall. 50Irid." for 550 parts pure platinum, 350 parts palladium and 50 parts iridum
Yellow Gold
The gold carats normally used in men's wedding rings are 9kt, 14kt and 18kt.
The higher the proportion of gold used in the final metal, the more valuable and expensive the metal will be. So all other things being the same, an 18kt ring will be more expensive than a 14kt ring and a 14kt ring will be more expensive than a 9kt ring.
9kt gold contains 37.5% pure gold (375 parts per thousand parts).
14kt gold contains 58.5% pre gold (585 parts per thousand parts).
18kt gold contains 75% pure gold (750 parts per thousand parts).
Jewelry is normally stamped with a marking to show the type of gold -
For 9kt gold the stamp will normally be either the number 375, 9kt, 9kt or 9K.
For 14kt gold the stamp will normally be either the number 585, 14kt, 14kt or 14K.
For 18kt gold the stamp will normally be either the number 750, 18kt, 18kt or 18K.
For 22kt gold the stamp will normally be either the number 916, 22kt, 22kt or 22K.
Gold Alloys - Why Are Other Metals Mixed With Gold?
Colored gold alloys are just as "real" as their golden colored counterparts. Pure gold is generally too soft to be used for jewelry, so other metals are nearly always added to it, no matter which color of gold is being prepped for jewelry making.
Chances are the ring on your finger is marked 18K, 14K, or 10K to indicate how much pure gold is present in the mix. The K stands for karat, the system used to state how much pure gold is found in an item.You'll find examples of pure gold jewelry, but pure gold is soft and isn't practical for daily wear. Other metals are mixed with it to make it more durable (and to lower its cost).Adding other metals to the mix also allows metallurgists to change the color of gold.
Colors:
1. White Gold - Palladium or nickel can be added to create white gold
2. Rose Gold - Adding copper produces a rose or pink tint
3. Green Gold - Adding silver gives gold a greenish cast
4. Purple Gold - Adding aluminum creates a brittle purple gold
5. Blue Gold - When indium or gallium is added to gold, a blue color can result
Some metals like aluminum and titanium can be anodized to create colors. The anodizing process creates a thin oxide layer. Aluminum and titanium films produced by anodizing can form thin, transparent coatings that produce interference effects in reflected light. The colors are applied using a bath, a brush, or a sponge, with the voltage applied determining the final color. Another anodizing application, particularly in aluminum, is the formation of thick, porous coatings that can absorb dyes to produce intense colors.Gold can be colored by creating surface oxide layers. Because gold does not oxidize in its pure form, base metals have to be added to create blue, brown, and black gold.
When metals are added to the gold the result is an alloy, a blended mixture of the metals that you can think of as a very expensive cake batter. Solid gold is a term that can be used to describe an item that's at least 10K (in the US) gold all the way through. Even though it's a gold alloy--18K, 14K, or anything down to 10K--it can be called solid gold.
Gold Filled Jewelry
Newer gold filled items have markings that indicate how much and what type of gold was used for the layer. A marking that says 1/20 12K G.F. means that the jewelry is at least 1/20th 12K gold by weight.
Gold Plated Jewelry
The gold layer in gold plated jewelry is typically thinner than the gold in gold filled jewelry, so it usually wears away more quickly. Plating is done in different ways.
You might see terms such as gold washed used to describe a very thin layer of gold--one that won't be very durable.
Gold Karat Markings · 24K gold is pure gold(99.9%)
· 22K gold contains 22 parts gold and 2 parts of another metal(s), making it 91.6% gold.
· 18K gold contains 18 parts gold and 6 parts of another metal(s), making it 75% gold.
· 14K gold contains 14 parts gold and 10 parts of another metal(s), making it 58.3% gold.
· 12K gold contains 12 parts gold and 12 parts of another metal(s), making it 50% gold.
· 10K gold contains 10 parts gold and 14 parts another metal(s), making it 41.7% gold. 10K gold is the minimum karat designation that can still be called gold in the US.
Even 18K gold, with its 6 parts of another metal, gives jewelers the opportunity to play around with color.
White Gold Alloys · Nickel can be mixed with gold to create a white (or gray) color; it can cause dermatitis in people who are sensitive to nickel.
· Palladium is another metal used to create white gold alloys. Related to platinum, it is more expensive than nickel, but is less likely to cause allergic reactions than nickel.
Rose & Pink Gold Alloys · Copper is added to make gold-colored alloys, but additional copper creates pink and rose tones -- the more copper, the deeper the effect.
Green Gold Alloys Greenish shades are created by adding silver to gold.
White Gold
White gold is an alloy of gold and some white metals such as silver and palladium. White gold can be 18kt, 14kt, 9kt or any karat. For example, 18kt yellow gold is made by mixing 75% gold (750 parts per thousand) with 25% (250 parts per thousand) other metals such as copper and zinc. 18kt white gold is made by mixing 75% gold with 25% other metals such as silver and palladium. So the amount of gold is the same but the alloy is different.
Traditionally nickel was used in white gold, however, nickel is no longer used in most white gold made today as nickel can cause reactions with some people. We do not use nickel in our white gold
When white gold rings are new they are coated with another white metal called Rhodium. Rhodium is a metal very similar to platinum and Rhodium shares many of the properties of platinum including its white color.
The rhodium plating is used to make the white gold look more white. The natural color of white gold is actually a light grey color. The Rhodium is very white and very hard, but it does wear away eventually. To keep a white gold ring looking its best it should be re-rhodium plated approximately each 12 to 18 months. Most local jewelers are able to rhodium plate jewelry for a cost effective price.
Titanium
Titanium is a white metal, but unlike gold it is used in jewelry in almost its pure form (approximately 99% pure). Titanium is extremely long wearing. Its natural color is a gray color.
Titanium is very lightweight, so a titanium ring will feel much lighter than an 18kt gold ring and much lighter than a platinum ring.
Titanium is also 100% hypoallergenic.
Titanium also has a unique property which allows the titanium to be colored to bright colors such as blue, purple and black.
For the metal itself titanium is generally less expensive than 9kt white gold. However, because titanium is difficult to make jewelry with the labor costs of titanium can make the price of a titanium jewelry a little higher. Though white gold will still normally command a higher price than titanium.
Sterling silver
Sterling silver is an alloy of silver containing 92.5% by weight of silver and 7.5% by weight of other metals, usually copper. The sterling silverstandard has a minimum millesimal fineness of 925.
Fine silver (99.9% pure) is generally too soft for producing large functional objects; therefore, the silver is usually alloyed with copper to give it strength, while at the same time preserving the ductility and beauty of the precious metal. Other metals can replace the copper, usually with the intent to improve various properties of the basic sterling alloy such as reducing casting porosity, eliminating firescale, and increasing resistance to tarnish. These replacement metals include germanium, zinc and platinum, as well as a variety of other additives, including silicon and boron. A number of alloys, such as Argentium sterling silver have appeared in recent years, formulated to lessen firescale or to inhibit tarnish, and this has sparked heavy competition among the various manufacturers, who are rushing to make claims of having the best formulation. However, no one alloy has emerged to replace copper as the industry standard, and alloy development is a very active area.
Tungsten Carbide
Tungsten carbide, also referred to simply as tungsten, is a very hard, strong and durable metal. It's also quite heavy.
Tungsten has a characteristic unique to this special metal - tungsten is highly scratch resistant.
Unlike gold, platinum and even titanium, tungsten rings do not scratch with everyday wear like the other metals do.
It is technically possible to scratch tungsten, though only with objects that are harder than tungsten. So that leaves diamonds, sapphires, rubies and ceramic. Though unless you dragged the tip of a loose diamond along the tungsten, the metal will stay scratch resistant.
Having a wedding band that's scratch resistant offers a lot of advantages.
Tungsten always looks new and bright and shiny. It doesn't need the polishing maintenance that gold, platinum and titanium rings do.
stainless steel
In metallurgy, stainless steel, also known as inox steel or inox, is defined as a steel alloy with a minimum of 11% chromium content by mass.Stainless steel does not stain, corrode, or rust as easily as ordinary steel (it stains less, but it is not stain-proof).It is also calledcorrosion-resistant steel or CRES when the alloy type and grade are not detailed, particularly in the aviation industry. There are different grades and surface finishes of stainless steel to suit the environment to which the material will be subjected in its lifetime. Common uses of stainless steel are cutlery and watch cases and bands.
Stainless steel differs from carbon steel by the amount of chromium present. Carbon steel rusts when exposed to air and moisture. This iron oxide film (the rust) is active and accelerates corrosion by forming more iron oxide. Stainless steels have sufficient amounts of chromium present so that a passive film of chromium oxide forms which prevents further surface corrosion and blocks corrosion from spreading into the metal's internal structure.
ref:
http://gilletts.com.au/information.php?info_id=39#color
http://en.wikipedia.org/wiki/Precious_metal
http://jewelry.about.com/od/platinumjewelry/a/platinum_faq.htm
http://jewelry.about.com/od/jewelrymetals/a/gold_jewelry.htm
