There is a wonderful array of choice available in gemstones. We'll be adding a section here about some of the options you have amongst coloured stones. Here's a site for you to view on that subject in the meanwhile: http://www.gemstone.org/
The key to a diamond's value is its rarity, and no two diamonds are alike. Rarity is determined by a diamond's unique characteristics as measured by the Four Cs: Cut, Color, Clarity and Carat Weight. Using these criteria, a small diamond of exceptional quality will likely be more valuable than a larger diamond of lower quality.
Diamonds are weighed using metric carats. Just as a dollar is divided into 100 pennies, a carat is divided into 100 points. This means that a diamond of 50 points weighs 0.50 carats or ½ carat. A ¼ carat diamond weighs 25 points and so on.
Created by nature, most diamonds contain unique birthmarks called inclusions. Diamonds with few birthmarks are rare and rarity affects value. The Gemological Institute of Americas (GIA) grading system for clarity has been adopted by almost all Canadian gemologists and jewellers. In the GIA scale diamonds are given a clarity grade that ranges from flawless (F) to those with very very slight inclusions (VVS), very slight inclusions (VS), slight inclusions (SI) to those with inclusions visible to even the untrained eye (I). Within each of these grades there are subcategories of 1 (better) and 2 (lesser). For stones, there are 3 subcategories. An I-3 stone is the worst and is, generally, a pretty ugly customer. Most diamonds sold in commercial jewellery are SI-2 to I-1.
The Gemological Institute of Americas (GIA) grading system for colour has been adopted by almost all Canadian gemologists and jewellers The GIA Diamond Grading System uses letters to represent colors beginning with D (colorless). In jewellery grade stones the colours then range down through E, F, G, H, I, J and K. The advancing letters describe stones with increasingly noticeable yellow, brown or grayish tinting. Most commercially sold diamond is in the H-I range. Fancy colour diamonds (such as canary yellow stones) are graded for colour separately.
The mere fact that there are traditionally 58 tiny facets in a diamond strikes many as little short of miraculous. But this precision is essential to the potential beauty of a diamond. The brilliance, fire, and sparkle that makes diamonds beautiful depends more on cut than anything else. Recognition is given to the superior cutting being applied to Canadian diamonds. The GIA continues to bicker about how to describe this attribute so there is still no internationally recognized grades for cut as there are for color and clarity.
Cut is one aspect that even the untrained eye will notice, especially in low light or when the stone is a bit dirty (as in real life conditions). You get your best cost benefit ratio when you choose a stone that is cut properly. Ask an experienced and trusted jeweller to help you do this.