Real diamonds will cut glass, though there is speculation that some fake diamonds can cut glass, and that you can damage a real diamond by cutting glass with it. Another way to tell is to hold the diamond up in the light. If you see any orange color from the diamond, it is fake, as real diamonds have every color EXCEPT orange.
Yes, you can buy fake diamonds.
Yes, diamonds can cut glass, because diamonds are harder than glass.
A proper glass cutter will be tipped with real diamond. A fake diamond may be used to cut something in an attempt to prove that it is not fake. Take your jewelery to a local jeweler to test the stone; that will help you determine whether or not the diamond is fake. Swiping glass with anything except a cleaning cloth could be considered vandalism.
No diamond is fake; but there are fake diamonds. Because natural diamonds are expensive and engaging to the human eye, many people want to own and wear diamonds, so a fake diamond can be substituted in the place of a real stone.
Imitation diamonds or fake diamonds are also known as faux diamonds. Or "simulant" as used by the industry insiders. It refers to materials, such as CZ, that look like another gem.
Retro diamonds are basically fake diamonds.
Yes, diamonds can cut glass. Glass can also cut glass.
No. Diamonds cut glass because diamonds are harder than glass. Quartz is not as hard as diamond.
When describing diamonds, glass is probably not as common as ice.
You can ask for CZs, crystals, glass, ice and find what you're looking for. Moissanite can also pass very successfully for diamond. ===== Keep in mind that De Beers would like man-made diamonds classified as "fake" but they are definitely REAL. Man-made diamonds have the exact same chemical composition and structure as those dug out of the ground. Gem-quality diamonds grown in a lab can be chemically, physically and optically identical (and sometimes superior) to naturally occurring ones.
Crystals or glass are probably the least expensive material that attempts to appear diamond-like. An appropriate noun might be paste.