Here's why:

* Colorless: Calcite is often found in transparent or translucent forms, appearing colorless.

* Powdered form bubbles with acid: Calcite is a carbonate mineral. When you drop a drop of dilute hydrochloric acid (HCl) onto calcite, it reacts, releasing carbon dioxide gas which causes the characteristic bubbling.

Important Note: While other carbonate minerals can also react with acid, calcite is the most common and easily recognizable by its clear appearance and reaction with acid.