Mineral of the Month: Stibnite
by Bob Farrar
The Mineral of the Month for February is stibnite. Its name comes from the Greek word for this mineral stibi. Stibnite has no value as a gemstone, but is of increasing importance industrially, and well crystalized specimens are much sought after by collectors.
Stibnite consists of antimony sulfide, Sb2S3. It is typically metallic steel-gray in color, though it sometimes alters to stibiconite (antimony oxide) which forms a yellowish coating. Stibnite crystalizes in the orthorhombic system. Crystals are often well formed and may be elongated and needle-like or more compact and solid. Fibrous or massive material also occurs. Stibnite has an interesting property of well developed “gliding planes”. The atoms can move a defined distance within the basal plane. As a result, crystals may bend without fracturing. Crystals may be bent when they are found or may bend later. Other physical properties include a hardness of 2 and a specific gravity of 4.5. Good crystals of stibnite are distinctive enough to be readily recognized, but lower grade material may require a negative test for lead and other lab tests to distinguish them from certain sulfosalts and other minerals.
Stibnite is typically formed in the later stages of the deposition of minerals in hydrothermal ore veins. Perhaps the finest specimens ever found came from Shikoku, Japan, where brilliant, elongated crystals up to 60 cm long were found. Another classic locality is Cavnic, Romania, known for beautiful sprays of needle-like crystals. Commonly seen on the market today are large crystals from several localities in China. In this country, some of the best crystals, up to 17 cm, came from Manhattan, Nevada. Small crystals in a white matrix have been found at Graves Mtn., Georgia. Other notable localities include Mexico, Kyrgyzstan, Slovakia, Italy, and France.
Stibnite is becoming increasingly important as an ore of antimony. Antimony is a critical component in many types of batteries, which are needed for the transition to renewable energy sources. Recently, the Biden administration approved the reopening of the Stibnite Mine in Idaho to help meet demand for antimony in the US after China placed restrictions on the export of this element.
Stibnite is also a favorite of many mineral collectors. Large single crystals, as well as intricate clusters of small crystals, make beautiful display specimens. Stibnite is also common enough that interesting specimens can often be had without a great expenditure of money.
by Bob Farrar
The Mineral of the Month for February is stibnite. Its name comes from the Greek word for this mineral stibi. Stibnite has no value as a gemstone, but is of increasing importance industrially, and well crystalized specimens are much sought after by collectors.
Stibnite consists of antimony sulfide, Sb2S3. It is typically metallic steel-gray in color, though it sometimes alters to stibiconite (antimony oxide) which forms a yellowish coating. Stibnite crystalizes in the orthorhombic system. Crystals are often well formed and may be elongated and needle-like or more compact and solid. Fibrous or massive material also occurs. Stibnite has an interesting property of well developed “gliding planes”. The atoms can move a defined distance within the basal plane. As a result, crystals may bend without fracturing. Crystals may be bent when they are found or may bend later. Other physical properties include a hardness of 2 and a specific gravity of 4.5. Good crystals of stibnite are distinctive enough to be readily recognized, but lower grade material may require a negative test for lead and other lab tests to distinguish them from certain sulfosalts and other minerals.
Stibnite is typically formed in the later stages of the deposition of minerals in hydrothermal ore veins. Perhaps the finest specimens ever found came from Shikoku, Japan, where brilliant, elongated crystals up to 60 cm long were found. Another classic locality is Cavnic, Romania, known for beautiful sprays of needle-like crystals. Commonly seen on the market today are large crystals from several localities in China. In this country, some of the best crystals, up to 17 cm, came from Manhattan, Nevada. Small crystals in a white matrix have been found at Graves Mtn., Georgia. Other notable localities include Mexico, Kyrgyzstan, Slovakia, Italy, and France.
Stibnite is becoming increasingly important as an ore of antimony. Antimony is a critical component in many types of batteries, which are needed for the transition to renewable energy sources. Recently, the Biden administration approved the reopening of the Stibnite Mine in Idaho to help meet demand for antimony in the US after China placed restrictions on the export of this element.
Stibnite is also a favorite of many mineral collectors. Large single crystals, as well as intricate clusters of small crystals, make beautiful display specimens. Stibnite is also common enough that interesting specimens can often be had without a great expenditure of money.
Stibnite, Chun Si, Hunan, China. Bob Farrar specimen and photograph.
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Stibnite, Wu Ling Mine, Jiangxi, China. Bob Farrar specimen and photograph.
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