Amber
Composition: fossil resin. Crystal system: amorphous. Hardness: about 2.0 to 2.5. Specific gravity: variable, from 1.05 to 1.10. Luster: resinous. Color: brown, yellow, red, orange, and white. Streak: white to yellowish to gray. Cleavage: none. Fracture: conchoidal. Tenacity: brittle. Diaphaneity: transparent to translucent. Refractive index: variable, about 1.54. Burns with a sweet, piney odor.
Rich brown to yellowish amber has been found near Eagle Pass, Maverick County, in Cretaceous coal and on Terlingua Creek, Brewster County. Although much of this material is translucent and the quality suitable for lapidary purposes, the pieces are seldom more than a fraction of an inch in diameter.
Occasional finds of poor quality brownish amber have been reported from the Tertiary formations of the Gulf Coastal Plain, but thus far no gem quality material has been found.
The softness of amber limits its use to brooches, necklaces, and other jewelry that is relatively safe from abrasion.