_Composition_: Be₃Al₂(SiO)₆. _Crystal system_: hexagonal. _Hardness_:
7.5 to 8.0. _Specific gravity_: 2.63 to 2.80. _Luster_: vitreous.
_Color_: pale blue, blue, green, yellow, brownish, pink, and
colorless. _Streak_: white. _Cleavage_: one direction, very imperfect.
_Fracture_: conchoidal to uneven. _Tenacity_: brittle. _Diaphaneity_:
transparent to subtranslucent. _Refractive index_: 1.56 to 1.60.
_Dispersion_: low.
Gem-quality beryl has not been reported in Texas. A discussion of beryl
is included herein because the writer believes it likely that beryl of
gem quality will be found in Texas as a result of future investigations
and exploration.
Beryl crystals have been found in pegmatite dikes in Llano, Blanco, and
Gillespie counties. These crystals are commonly several inches long and
exceed 1 inch in diameter but are very badly fractured. Most of the
beryl crystals do not approach gem quality and are entirely unsuitable
for any lapidary use. The color of the crystals found thus far is
bluish, greenish, pinkish brown, yellowish, and colorless. Some very
tiny colorless beryl crystals have been found that are transparent, but
thus far such crystals have been too small to be cut into gems.
Fine blue beryl crystals have been found in the Franklin Mountains near
El Paso, Texas. Unfortunately, these crystals are so badly flawed and
fractured that they are not suitable for lapidary use.
It seems likely that careful prospecting of Texas pegmatites will reveal
at least some gem-quality beryl.