_Carnelian_ (translucent reddish chalcedony).—This variety of chalcedony in small quantities has been reported from near Van Horn, Hudspeth County. Small pieces of carnelian have been found in the gravels of the Rio Grande, but finds have been few and scattered. _Jasper_ (impure opaque or subtranslucent quartz).—Good green, yellow, red, and brown jasper has been found in the gravels of the Rio Grande at all of the localities that produce agate. The colors are quite vivid, and the material takes a fine polish. Some pieces of orbicular jasper (jasper with circular or eye-like markings) have been found in this material. These gravels commonly contain jasper as fragments that are suspended in clear chalcedony; this is called brecciated jasper and yields very handsome cabochons. Many of the west Texas agate localities also produce jasper in quantity. Good jasper has been reported from north of Brackettville, Kinney County. Jasper is a minor constituent of the stream gravels in many parts of the State. Sanidine _Composition_: KAlSi₃O₈; commonly contains some sodium. _Crystal system_: monoclinic. _Hardness_: 6. _Specific gravity_: 2.57 to 2.58. _Luster_: vitreous to pearly. _Color_: colorless, white, pale yellow, and gray. _Streak_: uncolored. _Cleavage_: three directions. _Fracture_: conchoidal to uneven. _Tenacity_: brittle. _Diaphaneity_: transparent to subtranslucent. _Refractive index_: 1.52 to 1.53. Some feldspars, including sanidine, show a nice blue sheen in reflected light parallel to certain crystallographic directions. Stones having this property are called moonstone. A clear yellowish sanidine showing an attractive blue sheen has been found in Brewster, Jeff Davis, and Presidio counties. The individual pieces are small, the average size being about one-eighth inch. The sanidine is found loose in the soil at some localities where it has weathered out of rhyolite, and specimens of the sanidine in the parent rock are not difficult to obtain. Very small cabochons can be cut from this material, but few lapidaries have done so because inexpensive larger pieces of moonstone can be obtained easily from foreign sources. However, the west Texas sanidine does show a blue sheen when cut and polished. Spinel _Composition_: MgAl₂O₄ (magnesium may be replaced in part by ferrous iron or manganese and the aluminum by ferric iron and chromium). _Crystal system_: isometric. _Hardness_: 8. _Specific gravity_: 3.5 to 4.1. _Luster_: vitreous to sub-metallic. _Color_: black, pink, red, blue, green, yellow, brown, and violet. _Streak_: white. _Cleavage_: one direction, imperfect. _Fracture_: conchoidal. _Tenacity_: brittle. _Diaphaneity_: transparent to opaque. _Refractive index_: variable, approximately 1.72 to 2.00.