Ojuela mine, The

Elsewhere in the district, hematite is the main constituent of the iron ores of the La Lucha mine near Dinamita, where it is found as large red masses near the contact between the Sarnoso Stock and limestone (Hoffmann, 1967).

Hemimorphite Zn^sub 4^Si^sub 2^O^sub 7^(OH)^sub 2^[middot]H^sub 2^O

Specimen-quality hemimorphite has always been found fairly abundantly in the Ojuela mine, where it occurs as a late-stage mineral in all oxidized zones of the deposit, from almost at the surface to just above the water table in the lower levels (Panczner, 1987). Colorless to snow-white, commonly very lustrous prismatic crystals and sheaflike aggregates of subparallel crystals reach 3 or 4 cm in length (Hoffmann, 1967; Bancroft, 1984); these can form aesthetically pleasing sprays on dark brown goethite matrix, or "bow-tie" formations composed of two crossing sheaves (Jones, 1970b). Hemimorphite crystals invariably occur on goethite (and are sometimes stained brown or yellow by it); associations, where present, include calcite, aurichalcite, rosasite and adamite. Colorless hemimorphite is sometimes seen as a coating on lath-like crystals and sprays of aurichalcite (Jones, 1970b), and encrusting cigar-shaped formations of goethite (Johnson, 1962).

Jones (1970b) commented on the relative abundance of fine Ojuela mine hemimorphite specimens on the mineral market, saluting the showy specimens with 8-cm crystals which were available at the 1970 Tucson Show. Since that time, however, new examples of this beautiful material have been largely absent from the market, and it is in general less well known than it deserves to be. The lustrous white sheaves of hemimorphite on goethite from Mapimi should not be confused with the bladed, hematite-stained white crystals from the Santa Eulalia district in Chihuahua which began to appear on the market in the early 1970's (White, 1971).

In general, San Carlos has been a good but sporadic source of excellent hemimorphite specimens. In 2001, between Levels 5 und 6, San Judas produced about 50 specimens representing some of the very best hemimorphite ever found in the Ojuela mine: deep vugs in goethite and flat matrix plates to 45 cm are covered with sprays, spheres and wheels of white, lustrous crystals to 5 cm individually. An extraordinary large cabinet specimen from this occurrence is in the Peter Megaw collection.

"Higginsite" See Conichalcite-Austinite

"Hydrohausmannite"

Hoffmann (1967) described "hydrohausmannitc" as occurring in grains and thin bands in the manganese ores of the district. This substance has subsequently proven to be a mixture of hausmannite and feitknechtite (Bayliss, 2000).

Hydrohetaerolite Zn^sub 2^Mn^sup 3+^^sub 4^O^sub 8^[middot]H^sub 2^O

Hydrohetaerolite forms elongated euhedral crystals to 8 mm in fractures in manganese ore, and masses of euhedral grains replacing cryptomelane (Hoffmann, 1967; Panczner, 1987). It is relatively common in the manganese ore of American Dos and San Juan Poniente in the Ojuela mine (Hoffmann, 1967).