You have an 8mm tie tack that weighs less than one of your 7mm tie tacks.
How can the large stone weigh less than the small stone?
1. The difference in weight could be because of the depth of the cut. The 7mm round cut gemstone may be cut 6mm deep and the 8mm only 4mm deep.
2. The difference could also be the same reason a 1 inch cube of Aluminum weighs less than a 1 inch cube of lead. The Corundum (Sapphire & Ruby) is one of the heaviest of the gemstones and Quartz (Amethyst & Citrine) one of the lightest. Here is the Specific Gravity of some popular gemstones. The higher the number the heavier the gemstone.
Fire Opal - 2.2, Amethyst - 2.6, Emerald - 2.8, Peridot - 3.2, Topaz - 3.4, Diamond - 3.5, Sapphire - 4.0, Zircon, 4.6
What is the difference between a lab created and a lab simulated gemstone?
Because of the high price of natural gemstones many gems sold today are made in a laboratory.
To be lab created the gem must be identical to the natural gemstone in every way; hardness, composition, luster, looks etc. The only difference between a lab created gemstone and a natural gemstone is that the natural gem may have flaws. The mineral Corundum (Aluminum Oxide) is easily made in a lab, therefore sapphires, rubies and padparadsha are common lab created gemstones.
Lab simulated gems are made to look like the real gem but do not have the same other qualities such as composition and hardness. Most lab simulated gems are made from cubic zerconia, (not to be confused with the gem zircon). The mineral Beryl (Berylium Aluminum Silicate) is difficult to make in the lab making lab created Emeralds are very expensive. Therefore inexpensive man made Emeralds are lab simulated.
*** These are laws in the US and Canada and jewelry dealers have to obide by them. However, people outside the US and Canada are not bound by them. That said, eBay has rules that bind their sellers to them however, it is a very hard rule to uphold. Your best bet is to email the seller before you bid on or buy the jewelry/gemstone. ***
Why are your 14k gold tie tacks so much more than the Sterling silver ones?
The price of gold has been rocketing upward for the last year or so. It is now close to $1,500 an ounce. Silver has also risen a lot in the last few months. This time last year it was at about $20.00 and ounce and is now close to $35.00 an ounce.
Even though silver has gone up at lot, you can see that it is only about 2% of the price of gold.
What is the difference between gold plated and gold filled?
Gold plated means the setting has a very thin layer of gold. The thickness of this plating has to be at least 0.000007 inches of gold. Any setting with less than this is "gold washed".
To be gold filled the setting has to have a layer of gold equal to at least 1/20 the weight of the setting. This means that the gold layer is much thicker and is less likely to wear off.