Raw (Rough) precious stones look more like rocks when compared to polished stones used in jewelry. Anyone interested in searching and identifying raw gemstones should first start by purchasing an illustrated guide or by looking at pictures of raw gemstones online. If there is a museum displaying the precious stones, minerals, and rocks found in its location and area, visiting it can also provide information about these stones. To identify a raw (Rough) gemstone, its mineral properties must be reviewed, its lines and brilliance studied. Each gemstone has its own unique qualities that it is categorized to aid in identification. Also, Read – What are Natural Stones, What are the Properties of Natural Stones?
How To Identify Raw Gemstones?
Raw gemstones are typical crystal structures that sparkle and shine when cut and polished. Minerals fall into five basic shape categories, and they are as follows:
- Massive minerals with no definite shape
- Botryoid minerals resembling a bunch of grapes
- Reniform shaped minerals resembling kidney shapes, such as hematite stone
- Tabular minerals with a flat crystalline shape
- Acicular minerals that look like fine, needle-like crystals
However, to check for traces of a raw gemstone, its stone should be rubbed behind a ceramic tile or similar unglazed material. The colored powder left behind by the stone is called its line. The line of the stone is usually, but not always, the same as the color of the gemstone. For example, hematite stone is black when polished, but leaves a red streak on unglazed porcelain or ceramics.
The brilliance of a gemstone refers to the surface of the stone when it reflects light. Gemstones can look dull or oily like butter, but not as shiny as glass. They can also be shiny and glass-like, metallic or silky, and non-reflective. For example, raw blue sapphires from Brazil look just like blue-gray rocks, but a blue sapphire from Africa has angled surfaces and a crystalline appearance in a bright midnight blue. Also, Read – What Are The Side Effects Of Aloe Vera?
Splitting in a rock track refers to the way the stone breaks along a surface. Gemstones are broken in one of several ways and they are as follows:
- Flat washers break in one piece
- Rhombus refraction occurs at diagonal angles in several planes.
- Cubic flakes refer to stones broken at right angles in three planes.
- Long blocks cause fractures in two planes
Stone color is not the best indicator of the jewelry hidden within the stone, but can sometimes use color to identify the stone. For example, rough tiger eyes look like small rectangular multi-colored banded blocks. Raw hematite can look like 3/4 inch gravel on a driveway and can be gray or dull solid black in angular shapes. Rough turquoise can appear as a turquoise blue band in an otherwise anonymous rock. However, there are gems with raw values found in the world, and some of them are as follows:
Amazonite is an alkali feldspar mineral, a potassium aluminum silicate, with a hardness of 6 to 6.5, and has green or blue-green triclinic prismatic crystals. It is named after the Amazon river in Brazil and can also be found in Colorado, India, Madagascar, Namibia, and Russia.
Amethyst is a member of the quartz family, has a hardness of 7, and has trigonal crystals. It occurs naturally or in every shade of irradiated purple. Amethyst is found in many parts of the world, including Brazil, Bolivia, Mexico, Africa, Canada, Russia, Europe, and the United States.
Aventurine is a member of the quartz family with a hardness of 7. It is a silicon dioxide mineral with a trigonal (hexagonal) structure and is crypto-crystalline. Its name comes from the Italian word Ventura, a type of glass discovered in the 1700s. Very similar in markings to iridescent and a Ventura glass, it is found in large deposits in Russia, India, and Brazil.
Calcite is a calcium carbonate mineral, one of the most abundant crystals in the world, with a hardness of 3 and available in various shapes and colors. Calcite crystals are found on every continent, but there are large deposits in Mexico. Sawtooth calcite is rare and is found in Florida. However, this stone is often made into cabochons or wired for jewelry. Also, Read – What is Fuchsite Stone? Properties and Benefits
Citrine is a member of the quartz family and is a silicon dioxide mineral. It has a hardness of 7 and a trigonal crystal system. Citrine can be found in any shade from yellow to dark amber. Its name derives from the French word citron, meaning lemon. Citrine deposits are found in Brazil, Africa, Madagascar, Spain, Russia, France, Scotland, and the United States.
Quartz crystal is a silicon dioxide crystal, has a hardness of 7, and has a triangular (hexagonal) crystal system. It is the most abundant mineral in the world and can be found on every continent and in almost every country. It got its name from the Greek ice, as some were thought to have frozen too hard to thaw in water.
Ruby and Sapphire
Ruby and sapphire are varieties of corundum and aluminum oxide with a hardness of 9. They have a triangular (hexagonal) crystal structure and all colors of corundum are sapphires, except red ruby. Because of its hardness, it was used as an abrasive after diamond and is still being used. Rubies and Sapphires are found in India, Sri Lanka, Cambodia, Thailand, Madagascar, Tanzania, Pakistan, Afghanistan, East Africa, Australia, Brazil, and the United States.
Emerald is from the Beryl family and is a beryllium aluminum silicate mineral with a hardness of 7.5 to 8. It has a triangular (hexagonal) crystal structure and its name comes from the Greek Smaragdos meaning green stone. Emeralds are found in Columbia, Brazil, Russia, Africa, and the United States.
Fluorite is a calcium fluoride crystal, with a hardness of 4, and growing cubic or octahedral in patterns. It has various colors such as colorless, green, purple, white, yellow, red, pink, and black. Fluorite glows vividly under ultraviolet light, hence its name. It is available in Germany, England, China, Argentina, and the United States.
Almost all garnets are varieties of aluminum silicate. They have a hardness of 6.5 to 7.5 and various crystal structures. There are six types of garnets: Rhodolite, Almandine, Spessartine, Grossular, Andradite, and Uvarovite. The name garnet comes from the Latin word Granatum and means pomegranate. Garnet varieties can be found in Africa, Sri Lanka, Brazil, Madagascar, Sweden, Mexico, Greenland, and the United States.
Syenite is an aluminum silicate mineral. The hardness measured along the crystal axis is 4.5, plus the hardness measured along the crystal is 6 to 7. It has a triclinic crystal structure and its flat, blade-like crystals range in color from blue, indigo, green, black, pink, white, yellow, or gray. It is found in Brazil, South Africa, Switzerland, Burma, Kenya, Mexico, and the United States.
Marble is a crystalline rock composed predominantly of calcite, dolomite, or serpentine minerals. It has a hardness of 3-4 and its colors vary depending on the impurities in the marble. Impurities can make marble green, red, blue, yellow, etc. may cause it. The highest grade of calcite marble is pure white, marble containing hematite is red, marble containing serpentine is green, and marble containing limonite is yellow. Marble shines very easily, it is used for countertops, sculptures, carvings, building pillars, wall parts, stairs, and flooring.
Mica is a mineral with perfect basal cleavage and can be divided into thin layers called mica. It contains chemically complex aluminum silicate and hydroxyl-containing alkalis. It crystallizes in a monoclinic system, some varieties may contain iron, magnesium, lithium, rarely fluorine, barium, manganese, and vanadium. Mica pegmatites have been found to occur in various shapes and sizes, mostly in the form of lenses.
Muscovite is the most common of all mica forms. Sheet mica is used in a number of electrical and electronic devices in different shapes and sizes. Muscovite is a common mineral found all over the world. The word Muscovite comes from an old Russian word for a type of glass, Muscovy-glass, and is derived from the Latin word micare, meaning shine.
Moonstone is a potassium aluminum silicate feldspar mineral. Its hardness is between 6 and 6.5 and it forms monoclinic and prismatic crystals. It got its name after the blue-white glow produced by the moon. It is found in Sri Lanka, Madagascar, Burma, Australia, India, and the United States.
Opal is hydrated silica material with a hardness of 5.5 to 6.5. Microscopic silica spheres bond together with water and additional silica to form opal. Some Opal’s exhibit fire, a play of color resulting from the packing of tiny silica spheres in such an orderly formation to cause light diffraction. It gave rise to the Latin Opalus and the Sanskrit Upala Opal. Opals are found in Mexico, Australia, Peru, Brazil, Guatemala, Honduras, Japan, Turkey, and the United States.
Peridot is a magnesium iron silicate mineral with a hardness of 7 and has an orthorhombic crystal structure. It is known by three names: Peridot, Peridot, Chrysolith, and Olivin. Peridot derives from the Greek word Peridona, meaning to give abundance, and the word Chrysolith means golden stone in Greek. Pyrite
Pyrite is an iron sulfide mineral. It has a hardness of 6 to 6.5 with a cubic, pyritohedral or octahedral crystal pattern. Pyrite is also known by the nickname stupid gold, as it resembles large gold nuggets. The name pyrite is derived from the Greek words pyrites lithos, meaning stone struck by fire. Pyrite is found all over the world, but in large deposits in Italy, Spain and Peru.
Jasper is a silicon dioxide member of the quartz family, has a hardness of 6.5 to 7, and has triangular (hexagonal) crystal patterns. Jasper got its name from a Greek word meaning speckled stone. Jasper can contain up to 20% impurities, which can give it different colors. Jasper is available all over the world.
Rose quartz is a silicon dioxide crystal and is a member of the quartz family. It has a hardness of 7 and has a triangular (hexagonal) crystal system. It is found in Brazil, Madagascar, India, and the United States, and is often carved and cut in cabochons.
Smoky quartz is the silicon dioxide member of the quartz family, with a hardness of 7 and a triangular (hexagonal) crystal pattern. It is transparent quartz that is naturally irradiated and gives a smoky color. It is available in many countries, including Brazil, Australia, Madagascar, Switzerland, and the United States.
Sodalite is a chloric sodium aluminum silicate, with a hardness of 5.5 to 6, and has an isometric crystal system of the rhombic dodecahedron. The name sodalite refers to the sodium content. It can be found in Brazil, Canada, Namibia, India, and the United States.
Topaz is an aluminum silicate fluoride hydroxide crystal with a hardness of 8 and an orthorhombic crystal structure. The name Topaz is derived from the word topazes, which is also the name of an island in the Red Sea, but Peridot is not found in Topaz on that island. Topaz comes in gold, blue, pink, brown, orange, and light colors and is often irradiated to produce a blue color.
Tourmaline is complex borosilicate with a hardness of 7 to 7.5 and has a triangular (hexagonal) crystal system. Black Tourmaline is also known as Schorl. It has the widest range of colors of any gemstone and can be found in Brazil, Pakistan, Africa, Afghanistan, and the United States.