The name is derived from the color - the yellow of the lemon - , although the most sought-after stones have a clear, radiant yellowish to brownish red. Like all crystal quartzes, the citrine has a hardness of 7 on the Mohs scale and is thus, to a large extent, insensitive to scratches. It won't immediately take offence at being knocked about either, since its cleavage properties are non-existent. Even if their refractive index is relatively low, the yellow stones have just that mellow, warm tone that seems to have captured the last glow of autumn. Like golden Rhine wine or sparkling Madeira, heavy and sweet, citrine jewellery shimmers and brings a hint of sunshine to those dull November days.
Aquamarine is one of our most popular and best-known gemstones, and distinguishes itself by many good qualities. It is almost as popular as the classics: ruby, sapphire and emerald. In fact it is related to the emerald, both belonging to the beryl family. The color of aquamarine, however, is usually more even than that of the emerald. Much more often than its famous green cousin, aquamarine is almost entirely free of inclusions. Aquamarine has good hardness (7.5 to 8 on the Mohs scale) and a wonderful shine. That hardness makes it very tough and protects it to a large extent from scratches. Iron is the substance which gives aquamarine its color, a color which ranges from an almost indiscernible pale blue to a strong sea-blue. The more intense the color of an aquamarine, the more value is put on it. Some aquamarines have a light, greenish shimmer; that too is a typical feature. However, it is a pure, clear blue that continues to epitomise the aquamarine, because it brings out so well the immaculate transparency and magnificent shine of this gemstone.
This gemstone has no fewer than three names: peridot, chrysolite, from the Greek gold stone, and olivine, for the peridot is the gemstone form of the mineral olivine. In the gemstone trade it is called peridot, derived from the Greek word peridona, which means something like to give richness. The peridot is one of the few gemstones which come in one color only. The rich, green color with the slight tinge of gold is caused by very fine traces of iron. From a chemical point of view, peridot is an iron magnesium silicate. The intensity of the color depends on the amount of iron actually present. The color itself can vary over all shades of yellowish green and olive, and even to a brownish green. Peridot is not particularly hard - only 6.5 to 7 on the Mohs scale - but it is easy to look after and fairly robust. Peridot cat's eyes and star peridot are particularly rare and precious.
In order to understand this variety of color, you will have to brush up your knowledge of gemmology a little: tourmalines are mixed crystals of aluminium boron silicate with a complex and changing composition. The mineral group is a fairly complex one. Even slight changes in the composition cause completely different colors. Crystals of only a single color are fairly rare; indeed the same crystal will often display various colors and various nuances of those colors. And the trademark of this gemstone is not only its great wealth of color, but also its marked dichroism. Depending on the angle from which you look at it, the color may be different or more or less intense. It is always at its most intense when viewed looking toward the main axis, a fact to which the cutter must pay great attention when lining up the cut. This gemstone has excellent wearing qualities and is easy to look after, for all tourmalines have a good hardness of 7 to 7.5 on the Mohs scale. So the tourmaline is an interesting gemstone in many ways.