Kids Love Rocks - A guide to rock collecting
[Home] [Learn About Rocks] [Physical Properties]

The Physical Properties of Minerals

Fluorapophyllite mineral on stilbite

Minerals are identified by analyzing their physical properties. Let’s learn about these properties and discover what they mean and how to determine them.

Start by reading the descriptions of each of the physical properties, then dig deeper by clicking on each of the links to learn more about each property.

Cleavage & Fracture

Cleavage and fracture are descriptions of how a mineral breaks into pieces. Cleavage describes how a mineral breaks into flat surfaces (usually one, two, three or four surfaces). Fracture describes how a mineral breaks into forms or shapes other than flat surfaces.


The hardness of a mineral is a way of describing how easy or difficult it is to scratch the mineral. It is used, in combination with the other physical properties, to help identify a mineral specimen. 


Luster is a description of the way a mineral surface looks when light reflects off of the surface.

Specific Gravity

Specific Gravity is a measure of the density of a mineral compared to the density of an equal volume of water.


Streak is the color of a mineral when it is crushed to a powder.



An Educational Site by:
Cold River Mining Company
246 Silver Street
Greenfield, MA 01301
Phone (413) 219-3315

About Us
Activity Books
Activity Kits
Contact Us
Free Projects
Guide to Collecting
Kids Fun Club

Learn About Rocks
Make New Friends
Online Store
Panning Opportunities
Photo Gallery
What to Collect
Where to Find Rocks