It looks like you’ve done some good homework so far, a good website for general info on Diamonds (their EDUCATION Pages) is Blue Nile = http://www.bluenile.com and you can use that website to check out pricing for unmounted diamonds as well… just type in your specifications for the 4Cs (Cut… Quality & Shape – Clarity – Colour – and Carat Size) and you can get an idea of what an individual diamond with those specifications are worth.
Generally speaking, it is CUT (Quality), COLOUR and CLARITY (in that order) that makes a Diamond Sparkle
Many couples though make the trade off between Colour & Clarity (stressing clarity) due to pricing. This isn’t a bad decision if one is on a budget, and wanting say a bigger stone.
When it comes to size, you’ll find that pricing jumps at the “traditional” mile markers… so .25 – .50 – .75 – 1.00 – 1.50 etc. So something to take into consideration.
Realistically, size differences are really small… so visually it is very hard to tell a .75 Diamond for example from a 1.00 one. It really is only when you get to larger jumps like 1.00 to 1.50, to 2.00 to 2.50 that one can “see” a lot of differences
Check out this page on Blue Nile and the link for Diamond Carat Size Chart = http://www.bluenile.com/ca/diamonds/diamond-carat-weight
NOTE – that you need to set your Browser / Printer appropriately so that it shows / prints in actual size.
And this Percentage Coverage Chart for more info..
If she has smallish fingers… she may just fine with a smaller carat size.
My own fingers are short and stubby (Size 7, longest finger is under 2-3/4 inches long… hand from wrist to tip, under 6 inches). When Mr TTR bought my ring, he gave me a choice of something in the 0.75 range or the 1.00 range, and I opted for the smaller one… and it looks fine IMO (photo posted below)… and I too had a lot of other bling happening on my ring.
As well… it is worth knowing that in the Diamond Industry, that when they say 1 Carat it is actually a range… in that in reality they deal in fractions… so anything in the .95 to 1.05 size is called a Carat (this is because it would be impossible to cut each and every Diamond to showcase its best features to just 1.00)
So in fact there are 3 levels in the range you are considering…
3/4 Carat (0.75) = anything between .69 and .82
7/8 Carat = anything between .83 and .94
1 Carat (1.00) = anything between .95 and 1.05
Here is a pic of my own E-Ring. Almost 2.00 CTW with a Feature Diamond that is 0.80 Good Cut Round Brilliant – SI1 Clarity – and F Colour. It glitters like all get out (reflection sparks all around whenever the light hits it). BUT sadly, like a lot of WBee Posters, the pics just don’t do it justice.
It is also a Conflict Free Canadian Diamond and GIA Certified (the 5th and 6th Cs), that are important factors for some people.
Hope this info helps… and good luck in your search for the perfect diamond, now that you’ve been lucky enough to find the PERFECT GIRL