Barite

Barite (spelled also baryte) is a barium-bearing mineral (BaSO₄). It is mined both as an industrial mineral and as an ore of barium. This is somewhat unusual situation. Another well-known mineral mined as an ore and industrial mineral is zircon. Barite as the main barium-bearing phase in the crust is not uncommon mineral.

Intergrown tabular crystals (rosette) from Morocco. Width of sample 10 cm.

Baryte is usually quite close to ideal composition although solid solution to celestine (SrSO₄) is possible. Pure mineral is colorless, white or gray, but impurities (mainly iron compounds but also sulfides and organic matter) often give it slight yellowish or reddish hue. Blue coloration is usually due to radiation by radium atoms (Ra may replace Ba in the crystal structure because they are similar in size).

Barite may occur in well-formed crystals grown in hydrothermal veins. In these veins it is often accompanied by galena and sphalerite — lead and zinc ores, respectively. Other minerals that commonly occur with baryte are pyrite, quartz, fluorite, carbonates and other sulfidic ore minerals.

In the majority of cases it is found in various mineral aggregates. The most notable ones are platy and intergrown rosettes which are called desert roses or barite roses (gypsum also forms similar rosettes). Barite from sedimentary rocks may resemble marble – light-colored, massive and crystalline, but it is easily recognizable by its weight. It is strikingly heavy (specific gravity about 4.5) for a mineral without metallic appearance (even the name baryte itself comes from Greek barys which means heavy). Crystals may be mistaken for feldspar, but again weight gives it away and it is also significantly softer mineral (hardness about 3 on Mohs scale). Calcite and barite crystals may look alike, but calcite reacts vigorously with dilute HCl while barite does not react. It also occurs in various sedimentary rocks as cavity-filling concretions. It may be a residual mineral in clayey sediments in weathered limestones (limestone dissolved and carried away, insoluble barite and clay left behind). Barite may be a cementing mineral in sandstones.

Crystals may be mistaken for other more common minerals like feldspar or calcite, but barite is much heavier. Width of sample 8 cm.

Barite is the principal ore of barium. Barium has very high number of applications. It is known to have more than 2000 industrial uses. However, the majority of barite mined is not used to extract barium. It is valuable in its native form because of high density. It is mostly used by oil & gas industry as an ingredient of drilling mud. This slurry is pumped into the drill stem to prevent gas and other fluids from entering the wellbore during drilling operations. The drilling mud also lubricates and cools the drilling bit and carries rock cuttings back to the surface, but that could be accomplished by any drilling fluid. It is added to the mud only to increase its density.

Barite may sometimes resemble marble. Width of the sample from Kazakhstan 14 cm.

One peculiar use is swallowing it in chemically purified form (blanc fixe) in substantial quantities to make the gastrointestinal tract (or throat) more visible in X-ray images. It is somewhat odd to think about that because barium compounds are usually very toxic. This practice is considered to be of low risk because barite is very insoluble and chemically inert mineral. Blanc fixe is also used as a filler in paper and cosmetics and as a pigment. Playing cards, for example, are filled with barite to make them heavier.

Barite concretions from the Cretaceous marine shale (Bearpaw Formation, Saskatchewan, Canada). Largest concretion is slightly over 4 cm in diameter. Photo taken by Howard Allen (see the comments).