You're quite welcome-- glad to help out. Here's a follow-up: If you dip silver in a concentrated ammonia-based window cleaner it will turn gray over time; platinum shouldn't do this. I don't really recommend this test because ammonia will actually dissolve silver.
And since you've been such good readers: Here's a quick-n-easy way to tell whether your diamonds are real... I use a 10x microscope, but any good magnifier will work as well: look carefully at where the edges of the facets meet. If they are sharp and straight, this is what you want-- a good sign. If they are ground, chipped, or scratched from wear, you've got something else... possibly a softer natural gem, but definitely NOT a diamond. If they are curved and not flat, you've got evidence of an underpaid forced-labor gemcutter working under stress to get these cheap fakes to market fast!
Additionally, true diamonds are pure carbon, and -love- to bask in oil and grease. Soap scum will build up on the back of a real diamond and stay there forever. In the ground natural oils from organics can also build up and coat a true diamond. If you have a cruddy-looking diamond wannabe, maybe it really is: scrub the tar off it with concentrated liquid dish soap and a good used toothbrush. (I hear toothpaste also helps.) Turpentine or acetone may be used sparingly, if needed. If it sparkles nicely afterwards, send a donation to the charity of your choice and accept my congratulations on finding a prize!
FYI: Diamonds are very hard but not indestructible. They can fracture and split under shock. Hitting one with a hammer to prove it is a diamond is NOT a good idea. Though they can scratch glass, there are a lot of other things that can (including some fakes) as well, so this is not a reliable test. An electronic tester is a good idea; you can probably find one on Ebay for around $100. These work by heating a probe; when you touch the probe to the sample, heat dissipates according to the thermal conductivity of the specimen. Diamonds have a high thermal conductivity (similar to metal) and the tester will measure this. I've heard it said that if you could fill your bathtub with diamonds and lay in it, you'd freeze to death as they suck the heat out of your body. (A possible reason they are sometimes referred to as 'ice'.) I still don't have enough diamonds to test this theory, but am working on it... :lol: