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.
Friday, May 27, 2011
Monday, May 23, 2011
Precious Beads Howlite
Precious beads howlite is a soft white opaque stone with black or gray inclusions. Coming from the class of silicates, it is composed from calcium borosilicate hydroxide. It was named after Henry How, the Canadian geologist who first discovered it in Windsor, Nova Scotia, in 1868. It is still found there, although in much smaller quantities than it has been in the past. Precious beads howlite is known for its wonderful final polish and its habit is nodular massive. It is frequently dyed blue as a turquoise imitation. Available colors are in brown streaks or markings and white with gray to black. Precious beads howlite has a dull luster and conchoidal fracture.
With a monoclinic crystal system and specific gravity in 2.5-2.6 range, Precious beads howlite is an inexpensive gemstone. Because it is so soft and permeable, it is easily dyed to look like more expensive gemstones such as turquoise (a dyed stone is pictured, right). It is stopped at 3.5 hardness level and has none dispersion. The abundance of large size, and its softness makes precious beads howlite a good stone for decorative objects such as small carvings or jewelry components. Precious beads howlite is also sold its natural state, sometimes under the misleading trade names of “white turquoise,” or “white buffalo stone.” With an absent cleavage, precious beads howlite can be carved as beads or cut en cabochon. The refractive index is 1.59 (spot) and birefringence is 0.022.
Precious beads howlite is found in evaporate deposits, along with other borate minerals. Precious beads howlite is found in Canada (in the eastern provinces of Nova Scotia, Newfoundland, and New Brunswick), and along the western coast of the United States (particularly California). Precious beads howlite forms in nodules that look almost like a head of cauliflower. The nodules are often interlaced with veins of black or brown weblike streaks, which adds to their character. Translucent crystals sometimes form on top of the nodules, however, this is fairly uncommon in natural gemstones, and usually only found in the material mined in Nova Scotia. Precious beads howlite may fluoresce brownish yellow or orange under shortwave UV light.
With a monoclinic crystal system and specific gravity in 2.5-2.6 range, Precious beads howlite is an inexpensive gemstone. Because it is so soft and permeable, it is easily dyed to look like more expensive gemstones such as turquoise (a dyed stone is pictured, right). It is stopped at 3.5 hardness level and has none dispersion. The abundance of large size, and its softness makes precious beads howlite a good stone for decorative objects such as small carvings or jewelry components. Precious beads howlite is also sold its natural state, sometimes under the misleading trade names of “white turquoise,” or “white buffalo stone.” With an absent cleavage, precious beads howlite can be carved as beads or cut en cabochon. The refractive index is 1.59 (spot) and birefringence is 0.022.
Precious beads howlite is found in evaporate deposits, along with other borate minerals. Precious beads howlite is found in Canada (in the eastern provinces of Nova Scotia, Newfoundland, and New Brunswick), and along the western coast of the United States (particularly California). Precious beads howlite forms in nodules that look almost like a head of cauliflower. The nodules are often interlaced with veins of black or brown weblike streaks, which adds to their character. Translucent crystals sometimes form on top of the nodules, however, this is fairly uncommon in natural gemstones, and usually only found in the material mined in Nova Scotia. Precious beads howlite may fluoresce brownish yellow or orange under shortwave UV light.
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