Tellurium, New Mexico

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Volume 17, pages 491-492, 1932

NATIVE TELLURIUM FROM NORTHWEST OF SILVER CITY, NEW MEXICO

GERALD J. BALLMER, Santa Rita, New Mexico.

The writer has identified native tellurium as one of several minerals in vein material collected at a gold prospect located in Grant County, New Mexico, at a locality about 41 miles northwest of Silver City and 12 miles south-southeast of Mogollon.

The vein, which occurs as a fissure filling in quartz latite, is 12 inches wide and has been opened to a depth of about 135 feet. It is composed principally of quartz and fluorite, the other minerals noted being bismuthinite, pyrite, and tellurium. Assays show that the ore carries gold, but no more than a trace of silver, noteworthy amounts of which are present in the ores of the Mogollon district.

Many openings and cavities occur in the quartz of the vein. Some of these cavities are lined with druses of minute quartz crystals, others with several layers of pyrite, then filled with tellurium, and still others are filled with tellurium alone without the lining of pyrite. The tellurium occurs in irregular ovoid bodies of various sizes, the maximum measured being 18 mm. in length and 8 mm. in width. From the above description it appears that the first minerals to be deposited were quartz and fluorite, followed by a period of pyrite and quartz, and last of all tellurium. It is probable that the bismuthinite and gold are contemporaneous with the tellurium.

Examined under the microscope the section shows the tellurium as a tin-white mineral with metallic luster and strongly marked anisotropism. The hardness of the mineral is approximately B of the standard scale, and a careful determination shows its specific gravity to be 6.188.

Etching tests gave the following results which check with those recorded by Davy and Farnham but not entirely with Short's table which shows that HCl fumes tarnish the polished surface.

     HNO₃ (1:1), effervesces vigorously and stains dark gray.
     HCl (1:1), negative.
     KCN (20%), negative.
     FeCl₃ (20%), slowly tarnishes brownish gray.
     KOH (40%), negative. HgCl₂ (5%), negative.

The writer is indebted to Mr. J. J. Jones, Chief Chemist, Hurley, New Mexico, for the appended chemical analysis for which about 1.5 grams of carefully selected material was furnished.

	PER CENT	INSOLUBLE DEDUCTED
Insoluble	7.70	------
Te	87.00	94.28
S	1.85	2.01
Bi	3.12	3.38
	99.67	99.67

So far as the writer has been able to determine this occurrence of native tellurium is the first to be mentioned in the state. Tetradymite, or probably more properly named, tellurobismuthite, has been reported from Hachita, New Mexico.¹

1 Short, M N., and Henderson, E. P., Tetradymite from Hachita, New Mexico: Amer. Mineral., Vol. 11, No. 11, Nov. 1926, pp. 316-317.