Fig. 20 Biotite, demonstrating the perfect cleavage parallel to the crystal sheet

8. Random breakage of a mineral along no particular orientation is referred to as its fracture. Quartz and some other similar silicate minerals break along characteristic curved surfaces that look like slightly concave, circular seashells. These are called conchoidal fractures and can also be found along chipped edges of window glass.

Fig. 21 Conchoidal fracture

9. Some minerals have very distinctive taste qualities that facilitate their immediate identification. Rock salt (halite) and sylvite are two minerals with distinctive tastes.

10. A few minerals respond to common chemical reagents. Calcite responds to hydrochloric acid. Dolomite responds weakly to hot hydrochloric acid but reacts more when it is powered.

11. Radioactive minerals emit particles that activate various types of detectors and counters.

(Geology Link- http://college.hmco.com\geology\resources….)