Here's why:

* Colorless: Calcite can be colorless or white, although it can also come in other colors depending on impurities.

* Powdered: Calcite is relatively soft and can be easily powdered.

* Bubbles with acid: Calcite reacts with dilute acids (like hydrochloric acid) to release carbon dioxide gas, which forms the bubbles.

This reaction is a common test for identifying calcite.