Prehnite

Prehnite’s bright, almost luminescent, swirling green colors (reminiscent of Jade), mesmerizing clarity and striking luster, make it an extremely attractive collector’s gem. In his book, “Gemstones of the World,” Walter Schumann describes Prehnite as a transparent to translucent gemstone, which accounts for its “cloudy” appearance. This is totally normal and like many gemstones, its distinctive appearance is key to its appeal. While its main colors are a range of pleasant greens that are often unique to Prehnite, yellow, gray, colorless or white varieties also exist. Prehnite has some interesting common names including “grape jade” (in China it is called “putao yu,” meaning grape jade, due to crystal formations that look like a bunch of grapes), “cape emerald” (for the location of its discovery and visual similarities to Emeralds) and “prediction stone” (see above). Prehnite is usually found in cavities along fractures of basalt. The Australian deposits occur in scattered outcrops of Antrim Plateau Volcanics of early Cambrian age (about 570 million years old) and consist of massive basalt up to 197 feet thick. Although the primary Australian deposits cover thousands of square miles in the east Kimberley (Western Australia) and the adjoining Northern Territory, gem quality Prehnite is very scarce. With about 90% of the world’s reserves of this beautiful green gem, most of the Prehnite you’ll see on GemsTV hails from Australia.

Fluorite

Due to its glassy luster Fluorite is highly coveted. Fluorite is the natural crystalline form of calcium fluoride and often forms beautiful cube-shaped crystals. It is a transparent to translucent mineral. When pure, Fluorite is colorless; however, it usually contains impurities that color it. The most common colors are violet, blue, green, yellow, brown, pink and bluish black. Arguably, the most popular color for Fluorite is a deep purple that can rival Amethyst in its finest examples. Indeed Fluorite/Amethyst comparisons are often used to show that color cannot be relied upon as a gemstone identification test. An eye catching phenomenon of Fluorite is its distinctive multicolor banding. Chunky Fluorite bead strands optimize this exceptional effect. Interestingly, the “blue john” variety mined in England that possesses curved bands of blue purple, violet, yellow and white has been used as an ornamental gem since Roman times. Color Change Fluorite is mined in Bihar, India and shows a dramatic change from green to purple. Color change gems are those that distinctly change their color when viewed under two different light sources.

Demantoid

The demantoid is one of the most brilliant gemstones that exist, yet until recently it was little known except among collectors and gemstone lovers. Strictly speaking it is a green garnet, or rather the star of the green garnets. Not without reason does it bear a name which means 'diamond-like'. The name comes from the Dutch and makes reference to the outstanding quality of this gem, its incomparable brilliance and fire. Some gemstone lovers claim that a demantoid will continue to glow even in the shade. The demantoid belongs to the large gemstone family of the garnets, and is actually a variety of the garnet mineral andradite. But it is more than that: it is the most expensive kind of garnet and one of the most precious of all gemstones. It is highly esteemed on account of its rarity coupled with that incredible luminosity. For the latter, at least, there is a plausible explanation: the demantoid has an extremely high refraction (refractive index 1.880 to 1.889). Yet its high dispersion is also remarkable, in other words its ability to split the light which comes in through the facets and break it down into all the colours of the rainbow. The demantoid is a master of this, and does it even better than the diamond.

Spessartite

Within a very short time, this beautiful gemstone had shot up into the firmament of the international jewellery scene like a rocket. As to the name, there had been a certain amount of wrangling among gemmologists and gemstone dealers. Some called the brilliant orange to orange-red beauties 'Kunene spessartines', after the place where they had been found, whilst others spoke of 'hollandines'. But fairly quickly, the illustrative name 'mandarin garnet' began to prevail in international trade. That was the name by which the fiery orange gemstone was known when it began its conquest of the world. It was a fitting name, and it is the one which has remained to this day. Fortunately, that unique find on the Kunene River was not the only one of its kind. In about April 1994, more orange spessartines appeared in the trade, this time from Nigeria. As far as their colour and their brilliance went they were very similar to the mandarin garnets from Namibia, even if the experienced specialist was able to discern some subtle differences. They were found right down in the south-west corner of Nigeria, not far from neighbouring Benin. The mine is in a river-bed in the bush. During the rainy season it is necessary to pump the water out of the pits. Garnet specialist Thomas Lind of Idar-Oberstein was thrilled by the attractiveness of the new find: "There are some beautiful, radiant orange mandarin garnets from Nigeria in the trade, and among them there are, again and again, stones in sizes of over 1 carat. I am glad to say that they enhance what is being offered in the trade, and that the supply of this gemstone, which was once so rare, has stabilised in the meantime." Now, mandarin garnets are once again available in reliable quantities, even if top-quality stones are extremely rare.

Agate

Agate was highly valued as a talisman or amulet in ancient times. It was said to quench thirst and protect against fever. Persian magicians used agate to divert storms. A famous collection of two to four thousand agate bowls which was accumulated by Mithridates, king of Pontus, shows the enthusiasm with which agate was regarded. Agate bowls were also popular in the Byzantine Empire. Collecting agate bowls became common among European royalty during the Renaissance and many museums in Europe, including the Louvre, have spectacular examples. The mining of agate in the Nahe River valley in Germany, which was already documented in 1497, gave rise to the cutting-centre of Idar-Oberstein. Originally, the river was used to power the grinding-wheels. When the Nahe agate deposit had been exhausted, in the nineteenth century, Idar-Oberstein's cutters started to develop the agate deposits of Brazil, which sparked off exploration and the discovery of Brazil's rich deposits of amethyst, citrine, tourmaline, topaz, and other gemstones.