Beryl forms some of the most well known and prized gemstones. Varieties encompass the majority of the colour spectrum, from light to emerald green, light to deep blue, yellow, pink, purple, red, orange, brown and colorless. Beryl is transformed from its colourless state to one of its many hued varieties through trace elements of chromium and iron.
This mineral family widely occurs as prismatic crystals with a hexagonal cross section; they are generally found in pegmatites, ranging vastly in size. Crystals can range from single carats to extremely large and flawless examples displayed in museums.
Inclusions: The most common inclusions are long hollow tubes that run parallel to the long axis of the crystal. These may be liquid or gas filled inclusions.
Localities: Parts of Europe, Madagascar, Mozambique, south Africa, Zambia and the USA.
Mythicism: Ancient literature notes that Pliny the Elder, a Roman author, used powdered Beryl to cure eye injuries.
Chrysoberyl is one of the most interesting, yet least known, of the important gems. There are multiple varieties of Chrysoberyl, each with its own name and unique physical properties and their colours range from green, greenish yellow, and yellow to brown.
Alexandrite and Cat’s Eye are the most popular due to their peculiar and fascinating optical properties.
In spite of its name it is not actually a Beryl at all. The name is said to be from the Greek words chrysos, meaning golden and beryllos, which refers to the chemical element content of Beryllium.
Crystals are tabular or prismatic and are commonly twinned.
Inclusions: Stepped twin planes are occasionally present as well as needles and feathers.
Localities: Brazil, Madagascar
Mythicism: Known for thousands of years in Asia, it was highly valued for the protection it afforded from the “evil eye”.
Most people are familiar with Corundum; however, very few people know it by its mineral name. They are more familiar with the deep red coloured gemstone, Ruby and the blue specimen, Sapphire.
Colorless corundum is known as White Sapphire and any other color is known as Fancy sapphire.
Natural and synthetic corundum have a wide variety of industrious uses because of their toughness, hardness, and chemical stability. They are used to make industrial bearings, scratch-resistant windows for electronic instruments, wafers for circuit boards, and many other products.
"Emery boards" are a manicure and nail-care product that is made by gluing abrasive papers to a thin piece of cardboard. They obtained their name in the 1800s when crushed emery was used as the abrasive. Today's emery boards are not made with emery. Instead, many of them have a coarse side of synthetic corundum and a fine side of garnet abrasive.
Corundum has a vitreous to adamantine lustre and forms prismatic, tabular or rhombohedral crystals.
Inclusions: Corundum can be many colours but always has a white streak. If the streaks appear on more than two sides of the stone it creates the star shaped optical effect, asterism. These gems are then labelled Star Stones.
Localities: Africa, Kenya, Madagascar, Burma, Thailand and Sri Lanka.
Feldspar is by far the most abundant group of minerals in the earth's crust, forming about 60% of terrestrial rocks, gem quality, however, is rather rare. Feldspar forms directly from cooling magma and is a major component of granite and most other igneous rocks.
The entire feldspar group is divided into two main branches, the potassium feldspars: microcline and orthoclase, and the sodium/calcium feldspars known as the plagioclase. Feldspars tend to twin easily; one crystal can even be multiply twinned on the same plane, producing parallel layers of twinned crystals. They have two directions of cleavage at nearly right angles. Feldspars also tend to crystallise in igneous environments, but are also present in many metamorphic rocks.
Feldspars are primarily used in industrial applications for their alumina and alkali content.
Most of the products we use on a daily basis are made with feldspar: glass for drinking, glass for protection, fiberglass for insulation, the floor tiles and shower basins in our bathrooms, and the tableware from which we eat. Feldspar is part of our daily life.
The name "feldspar" is said to come from "field stone", because when Feldspar weathers, it releases large amounts of plant nutrients, such as potassium, which enrich the soil.
Localities: Italy, Turkey, America
Fluorite can be found in almost any colour, except for black or red.
The crystals formed by this mineral are cubes and octahedral and are often twinned. If broken, its perfect octahedral cleavage produces triangular shapes on the corners of the cubic crystals. Forms in hydrothermal veins and around hot springs. As it name suggests, it can be strongly fluorescent in ultraviolet light.
Localities: England, Switzerland, France, India, South Africa, Mexico and USA.
Garnets are a group that includes a number of different minerals, so appearance can vary widely.
They are found throughout the world in rocks of many types. The array of elements that compose its many species, as well as the varying conditions, are what help produce a considerable array of garnet gems. The one thing to connect all garnets is the crystal composition, they are all isometric and singularly symmetrical.
Hardness: 6.5 to 8.5
Inclusions: Garnet clarity depends on garnet type
Mythicism: Garnet was once said to cure melancholy and to warm the heart. In middle ages, knights would place Garnets on their shields to prevent injury.
The structure of opal is amorphous, so it does not have the long range characteristics of a crystal and it is the only gem mineral created in this way. It is a solidified jelly composed of silica and water. Precious opal is milky white, or black with a brilliant interplay of colours, commonly red, blue and yellow. The colours often change when heated and the gem fluoresces in ultraviolet light.
The name comes from the Sanskrit word upala, which means precious stone.
Localities: Opal was first found on the White Cliffs, Australia in 1889 and the country has been the biggest producer ever since.
One of the most common minerals, quartz forms hexagonal prisms. Quartz can be divided into two groups, single crystals and those found as masses with a minute or microscopic structure. It is also the source of many gemstones such as onyx, jasper and bloodstone. The colour is amazingly variable, and quartz may be white, grey, red, purple, pink, yellow, green, brown and black, as well as being colourless. the different varieties of quartz are found in a wide range of countries and environments.
Localities: The most commercially used comes from Brazil.
Scapolite ranges in colour from pink, violet, yellow to colourless. The colour range is a reflection of the amounts of sodium and calcium found present.
Crystals are found in prisms that resemble sticks, giving rise to the name “scapolite”, derived from the Greek word scapos. most crystals have rough or uneven faces.
Localities: Burma, Brazil, Canada, Kenya and Madagascar
A characteristic of this mineral is that it is infusible and synthetic spinel can easily masquerade as other gemstones. It is usually used to imitate other gemstones rather than act as spinel itself.
The red spinel is an orange red colour, like ruby, owes it colour to chromium.
This mineral forms as octahedral and sometimes cubic or dodecahedral crystals.
Localities: You can also find blue spinel, this is not quite the same blue as sapphire but the brightest are found in Sri Lanka. Red spinel comes from Sri Lanka, Burma and Pakistan.