_Composition_: hydrous phosphate of aluminum and copper. _Crystal
system_: triclinic. _Hardness_: 5 to 6. _Specific gravity_: variable,
2.6 to about 2.8. _Luster_: dull, sometimes waxy. _Color_: sky blue to
greenish blue. _Streak_: white to greenish. _Cleavage_: none in
massive material, two directions in crystals. _Fracture_: conchoidal
to subconchoidal. _Tenacity_: brittle. _Diaphaneity_: subtranslucent
to opaque. _Refractive index_: 1.61 to 1.65.
Turquoise of good sky-blue to greenish-blue color has been found a few
miles southwest of Van Horn, Culberson County. Several shallow pits were
dug at this locality about 1910; however, the amount of turquoise
produced was small. The main occurrence of the turquoise was in seams
about 1 millimeter thick along joints in the fine-grained rocks of this
area. Persons who have visited Culberson County more recently report
that even minute traces of the turquoise are now difficult to find at
the old prospect pits. However, further prospecting in the area might
yield some additional localities.
Small amounts of turquoise have been reported near El Paso, El Paso
County, and also in volcanic rocks near the Jeff Davis-Brewster County
line, north of Alpine.
A small amount of turquoise has been mined from several localities a few
miles northwest of Sierra Blanca in the Sierra Blanca Mountains of
Hudspeth County.