A shard
It mainly refers to gemstone, a cut rock or mineral.
This would be called a gemstone.
In an unpolished or a rough gemstone the reflection of light is poor. To take out the brilliance of a gemstone it has to be cut and polished. For a diamond RBC (round brilliant cut) takes out its true worth.
A rectangular gemstone shape is known as an "emerald cut." This cut is often used for emeralds, as well as other gemstones like diamonds, sapphires, and aquamarines. It features a rectangular shape with trimmed corners and step-cut facets.
No, emeralds are not hard enough to cut glass. Diamonds cut glass and they are the only gemstone with this capability.
A gemstone that has been cut and polished is called a faceted gemstone. This process enhances the gem's color, clarity, and sparkle by creating flat, polished surfaces known as facets.
The side of a cut jewel is called a facet. Facets are flat, polished surfaces that are cut into a gemstone to enhance its brilliance and sparkle. The number and arrangement of facets can vary depending on the cut of the gemstone.
That depends on what gemstone (diamond, ruby, etc.) it is, the size of it, the quality, and the cut.
The Hindi name for Labradorite gemstone is "कुक्कुटकाथू".
The crown
Yes.
A rare mineral that can be cut and polished could be called a gemstone.