First off, I'm not a gemologist. But I have gained a tiny bit of knowledge on the subject in the past few years working with Jewelry.I'm often asked the difference in certain"metals" and What are certain Stones..So here's a Little bit of what I know:
Just a note : 99.9% of ALL gemstones are treated in some way. There are Very Very Few that are totally natural.
These explainations are just "basic". There are always exceptions to the rules and this is just an "idea" of what to expect.
Garnets are usally totally natural {except for cutting and polishing} As are Chrome Diopside.
[And there are many many colors of garnet. Not just red!]
Apatite is also an untreated stone,But is sensitive and shouldn't be subjected to heat.
Topaz" is a stone that is routinely treated. Natural stones are usally yellowish/orangy {the Imperial} or Pink {precious pink}.
They are heated to achieve different colors and also 'vaporized' with chemical particles to get ,what we call the "Mystic" effect.
"London blue" the deep rich blue topaz,is heated and irradiated.This process can take up to 2 years.The longer or more detailed
treatment,the more expensive this stone will be. These Treatments are much more complicated than I am explaining,But this is the best way that I know how to tell you. [ hope you ain't counting off for spelling either..LOL ]
"Most" Rubies are heated,some are fissure filled {which enhances the color and durabilty} An untreated Ruby can run in the 10's of thousands of dollars per carat. Sapphires are also heated to achieve the different colors.
Contrary to some ad's I have seen..There is NO SUCH THING as a RED sapphire.
Sapphire is composed of a material known as "corundum". RED corundum is simply "RUBY".....
And.."Lab Created Gemstones" are exactly the same as natural stones , "Phyically,Optically,and Chemically"
The only difference is.. they were not formed in nature,but in a lab using the same mineral componets.
Man-Made Stones, Such as Cubic Zirconia are totally FAKE.
Pearls are usally "cultured" now days. Man has a hand in this by placing a "seed" of some sort, a grain of sand maybe,into
the Mollusk {shellfish} But, the Mollusk itself, all alone, must make the pearl. This can take years ! Average size for a 'cultured' pearl is around 5-6mm. Altho ,some of the colored pearls,such as "peacock", are dyed. Natural pearls are USALLY white,cream,pink and sometimes lavander. South Sea Salt water pearls are the most sought after. {the majority of cultured pearls are freshwater}.
Diamonds are set apart from all other stones. They are graded differently,usally more expensive and for most of us,
hard to come by. In some cases they are cut and faceted by '6' different people. Which is something to think about,
ALL gems have to be mined, cut,polished,faceted and sometimes treated. That might explain some of the cost.
Metals :
Rhodium is the most expensive metal.Used primarilly to color or overlay another metal..such as "black rhodium"
Next is Platinum 950. Used to overlay and in some of the VERY high end jewelry.
Gold : 24k-usally used for overlay or inlay as in the pure state is very soft. 100% pure--(.999)
22k used mainly the same as 24k
18k used in High end jewelry,very durable.--(.750)
14k most well know formula--(.585)
10k first used in less expensive jewelry,But with the rise of gold prices,it can be expensive as well
9k Mostly used in European designs
Silver: Pure Silver -.999 or 99%
Argentium -.930 -93% silver or better --7% or less other metals
Sterling -.925-92.5% Silver --7.5% copper
Tibetan - .650-.700 or 65%-70% Silver ---30%-35% white copper
Alpacca - .500 -.550 or 50% -55% Silver ---45%-50% Nickel
There are 1000's of different gemstones and lots of different metals that are being used,But Maybe
this will be some help to you.If you have any questions,feel free to email me.I may just have to say" I don't know"..
But it never hurts to ask... Happy Shopping and God Bless !