Natural crystal indicolite is the blue variety of the tourmaline minerals elbaite and liddicoatite. Coming from the class of ring silicates, this gemstone has trigonal system and composed by complex borosilicate. It derives its name from the Latin for the indicum (indigo) plant, famed for its opulent blue colors. Natural crystal indicolite is commonly found in North America, Madagascar, Brazil, Namibia, Africa, Australia, and Sri Lanka. Colors are available in light green-blue through to deep blue. The fracture is uneven to subconchoidal.
Like all tourmalines, natural crystal indicolite can be beautifully set, and it wears well in almost any type of jewelry. Step cuts are most common. Natural crystal indicolite has 1.622-1.641 refractive index and specific gravity in range of 3.05-3.11. The habit is prisms with flattened terminations, sometimes needle-shaped of fibrous. Buyers need to ensure that the color is correct: natural crystal indicolite should be a light to dark, very saturated blue, many gems sold on the market are not true natural crystal indicolites. Small stones (between one and eight carats) are common, and stones up to even 15 carats are available. This gemstone has dispersion about 0.017 and the birefringence is 0.019. Larger stones tend to be collector’s items, but excellent stones that are up to 100 carats in weight are not unheard of. Natural crystal indicolite has vitreous luster and imperfect cleavage.
Natural crystal indicolite, the most unique natural gemstone, is pleochroic, meaning it can show different colors (or lighter and darker tones) when viewed from different angles. The hardness of natural crystal indicolite stopped at level 7-7.5. It is transparent to opaque and is found in igneous and metamorphic rocks, and best developed in pegmatites. A true natural crystal indicolite will be pure blue, but most range from light greenish blue, through to bright blue, and up to rich, dark blue. Although some material is very clean, natural crystal indicolite typically contains hollow tube inclusions, and cat’s eyes are not uncommon.
