Hubeite

Hubeite can be identified by its hardness of 5.5 on the Mohs scale, Dark brown to light brown in thinner crystals. color. Look for these key characteristics when examining specimens.

Hubeite typically appears in Dark brown to light brown in thinner crystals.. Color can vary depending on impurities and formation conditions.

Hubeite has a hardness of 5.5 on the Mohs scale. This gives it moderate hardness.

Hubeite is most common as aggregates of intergrown crystals (Fig.1) that are usually less than 5 mm across and that have individual crystals with well-developed faces that are as long as 1 mm (Hawthorne et al., 2002). The color ranges from pale to dark brown, depending on the crystal size (Fig.2). Other properties consist of a pale orange-brown streak, vitreous luster, non-fluorescence, and one good cleavage parallel to the c-axis. It is also brittle with conchoidal fracture, has a hardness of 5.5 in the Mohs scale and a specific gravity of 3.02 (Hawthorn et al., 2002). As for optical features, it is important to note that hubeite is strongly pleochroic, biaxial with an indeterminate optic sign and has a birefringence of 0.023 (γ-α) (Hawthorne et al., 2002).

Hubeite is mainly associated to a skarn assemblage with pink inesite, colorless apophyllite, quartz, pyrite and colorless-white calcite (Hawthorne et al., 2004). They all occur together at the Daye Mine. Usually hubeite appears in two different situations. It may occur as isolated aggregates of crystals perched on white quartz, or it may occur covering both sides of thick specimens, that are usually pink inesite and apophyllite (Hawthorne et al., 2002). Figures 3 and 4 illustrate both situations. The localities where ruizite is found, associated with apophyllite, inesite and pyrite as well, and there is no hubeite, which leads the conclusion that hubeite needs oxidized environments and sufficient concentration of iron to occur. The Daye mine is an iron ore deposit (Dingyu et al., 1982). This specific area is characterized by deposits of late Paleozoic carbonate rocks in contact with plutons aging between the middle Jurassic to middle Cretaceous (Dingyu et al., 1982). According to Dingyu et al. (1982), the iron rich magma injections are the main cause for the formation of the ore deposits of the region. These polymetallic deposits form a belt that crosses China in the west–east direction (Ottens, 2007). Curiously, the mine where hubeite was first found is in fact a wollastonite source for minerals collectors.

To analyze the composition, an electron microprobe was used in the wavelength-dispersion mode (Hawthorn et al., 2002). The quantity of (OH) and (H2O) was acquired by solid solution and refinement, based on previous work by Hawthorne et al., 1990. To assure the presence of (OH) and (H2O) groups, an infrared spectrum was also recorded (Hawthorn et al., 2002).