Very rare milarite crystals can occur in green and yellow colors. Transparent material can yield small but pleasant looking faceted gems for collectors.
Milarite belongs to the mineral group named after it. Sometimes called the osumilite group, this group also includes sugilite and other rarely faceted minerals, such as poudretteite and sogdianite.
Identifying Characteristics
Milarite was originally known as a green mineral, until fine yellow crystals were discovered in Mexico in 1968.
Some milarites may luminesce. Shortwave (SW) ultraviolet (UV) light may cause bluish white or greenish white fluorescence and phosphorescence, while longwave (LW) UV light may cause medium chalky green fluorescence and weak phosphorescence.
Guanajuato, Mexico produces yellow and yellow-green gem-quality crystals on matrix, and some larger Mexican crystals have transparent areas suitable for cutting.
Minas Gerais, Brazil and Tsumeb and the Erongo region in Namibia have also yielded small, facetable material.
Crystals can occur up to about 4 cm across, but facetable areas in such crystals are very small. Thus, stones over 1 carat could be considered large for the species.
With a hardness of 5.5 to 6 and no cleavage, milarites could make suitable jewelry stones if worn with protective settings. However, you’re more likely to find them — if at all — in mineral collections than jewelry collections.
Stay on the safe side and refrain from cleaning these rare gems in mechanical systems. Instead, use a soft brush, mild detergent, and warm water. Consult our gemstone jewelry care guide for more recommendations.