A white or silver blue iridescent haze displayed by moonstone and other gems.
Gem deposits found in water after they have been separated from the mother or host rock.
A M B E R more info
A prehistoric fossil resin that usually has plants and other debris, including insects trapped inside which then hardens over thousands of years, usually found underground in areas what used to be deep forest vegetation. (click the subject title for more indepth information)
An evaluation performed by a licensed gemologist to determine the value of a gem or item of jewelry.
A star effect displayed by certain gems with intersecting inclusions. (see 'rutiles')
The Spanish word for "rough", as in rough or raw gemstone and mineral material.
The most common form of gem cutting, in which the mineral is cut with a flat bottom and is rounded on top.
The unit of measure for the weight of a mineral. One carat is roughly equal to 200 milligrams, or five carats equal approximately one gram.
A metamorphic rock produced by the crushing and grinding of pre-existing rocks, that are still visible as crushed fragments.
Cat's eye effect produced by some gemstones when cut properly in cabochon form. (see 'rutiles')
The orderly geometric spatial arrangement of atoms in the internal organization of a mineral specimen.
The breakpoint or weakness of a gem, connected to its atomic structure. Most gems with perfect cleavage are more likely to break when being cut or faceted.
An important property used in the evaluation of a gem. The quality of a gem can be measured based on either the presence or the absence of color.
Color of Play
Same as above, usually used to describe the fire in an opal or fire agate.
Skeletal crystals that develop from supersaturated solutions, often in small cracks, often resembling plants or trees.
The ability of some gems to display a second color when viewed from a different angle.
The splitting of light as it enters a gemstone. Also called a stone's "fire".
A stone made of two components, generally held together with a clear adhesive.
Stalagmites or stalactites.
Druse or Drusy
The crystal coated surface of a rock specimen.
A stone, geode or quartz with the center cavity containing encased water.
The cut and polished part of a gemstone.
The process of cutting a gemstone to have multiple polished, angled flat surfaces. This process is designed to bring out the brilliance of a gem.
Characteristic of certain gemstones that disperse white light into a rainbow of colors. It is a primary characteristic of gem diamonds, opals, fire agate, spectrolite and other stones.
Temporary emissions of radiation at different wavelengths (color) struck by light waves - long or short wave ultraviolet light.
Mineral deposits from rivers.
A substance made up of thin leaves, like mica.
A break with an uneven or irregular surface crack.
A mineral crystal or natural gemstone that has been cut and polished. In general, any attractive and relatively flawless mineral crystal can be cut into a gem.
A person who has successfully completed recognized courses in gemology and has proven skills in identifying and evaluating gem materials.
The science, art and profession of identifying and evaluating gemstones. A branch of mineralogy.
A hollow rock cavity usually containing some form of one or more quartz gemstone. Amethyst and Peridot are sometimes found in geodes.
A unit of measurement of weight used to express the weight of a gem. Just over 28 grams equals one ounce. (one thousand milligrams equal one gram)
The application of heat to a gemstone for the purpose of improving its depth or richness of color.
Any type of material trapped inside a mineral during its formation. Inclusions are generally other minerals or rocks, but can also be water, gas or petroleum based.
Rock formed by the solidification of magma from a volcano.
The play of color in a gemstone resulting from inclusions or layers of minerals.
Unit of measurement that indicates the quantity of fine gemstone specimens and minerals like diamonds or opals.
The Spanish word for "karat". (see above)
The metric measurement of 1,000 grams, or 2.2 pounds (standard measurement)
The art and practice of cutting gem stones and minerals.
A person who is a cutter, polisher or engraver of precious stones.
A quantity of raw materials or stones, the exact weight and amount can vary.
The Spanish word for "lot". (see above)
The outward appearance of a gem or organic material. Luster is most important especially when evaluating the quality of pearl.
Changes in rocks brought about by heat and pressure from in the rocks just below the surface.
Solid object that comes from outer space and falls to earth; made up of metal material, usually magnetic.
A person who studies the formation, occurrence, properties, composition and classification of mineral specimens.
A mineral-like substance that does not have a crystal structure and possesses a chemical composition that varies beyond the accepted range for a specific mineral.
An earth science focused on the chemistry, crystal structure and physical properties of minerals, their distribution and identification.
A natural, inorganic, solid compound having a specific chemical composition, formed through geological processes.
A person who excavates and searches for gemstone and mineral specimens.
The Spanish word for "miner". (see above)
Underground areas and caves where precious, semi-precious gemstones and minerals are excavated. The plural version is 'mine'.
The Spanish word for "mines". The plural translation is 'mina'. (see above)
Moh's Hardness Scale
The numerical scale developed by Friedrich Mohs in 1822 that assigns a rating to a gem according to its ability to resist scratching, with the hardest being 10 and the softest being 1.
The hardness of a mineral is an easy diagnostic test to perform to attempt to identify an unknown mineral. For example, if mineral X scratches mineral Y, and mineral Y does not scratch mineral X, then mineral X is harder than mineral Y. If mineral X and Y both scratch each other, then their hardness is equal or very similar.
Hardness is rounded off to the nearest half number. The 10 minerals in the scale are:
Mohs scale is very useful but it is not linear. The minerals chosen were selected only because of their popularity. Number 10 on the scale (diamond) is 140 times harder than number 9 (corundum), whereas 4 (fluorite) is only 1.11 times harder than 3 (calcite). A proportional measurement, called absolute hardness, was recently devised, but is currently only used by scientists who need the most accurate of results. The Mohs scale is the standard used by mineral collectors only.
The Mohs Hardness Scale is relative. Fluorite at 4 is not twice as hard as gypsum at 2; nor is the difference between calcite and fluorite similar to the difference between corundum and diamond. An absolute hardness scale looks a little different than the relative scale. Most minerals are close in hardness. But as hardness increases, the difference in hardness greatly increases as seen in the absolute hardness scale pictured here.
Using an absolute scale you can say that corundum is actually 4 times softer than diamond, not half as soft like the Mohs relative hardness scale shows.
A mineral, stone or organic material that can be cut and polished or otherwise treated for use as jewelry. A “precious” gemstone has beauty, durability and rarity, whereas a “semi-precious” gemstone has only one or two of these qualities.
O B S I D I A N more info
Obsidian is the result of volcanic lava coming in contact with water. Often the lava pours into a lake or ocean and is cooled quickly. This process produces a glassy texture in the resulting rock. Iron and magnesium give the obsidian a dark green to black color.
A variety of iridescence that is most often a light blue glow in color.
Not transparent or translucent.
Matter that is not technically a gemstone, but is derived from animal or plant life. Organic gems include amber, coral, ivory, pearl and tortoise shell among others.
A liquid coating that adds a pearl like luster to simulated pearls. It is derived from the scales of a herring fish.
Units of measurement to express the carat weight of a gem. One carat is equal to one hundred points.
Native material around a gemstone, like ironstone surrounding opal.
The quality of a gem that has beauty, durability and rarity.
Defined by the industry as gold, silver and platinum, the term 'precious' is still widely accepted to delineate metals.
When a gem or mineral is found resident in its original host or mother rock.
A person who cuts and polishes a variety of gemstones and minerals.
The Spanish word for "polisher". (see above)
Q U A R T Z more info
Formed from the two most abundant elements in the earth's crust: silicon and oxygen. Quartz has a high thermo-conductivity, which makes it feel cool to the touch. Historical records show the use of quartz crystal for decoration and jewelry for at least the past 4,000 years. Spiritually, they are also able to structure, store, amplify, focus, transmit and transform energy, which includes matter, thoughts, emotions and information. (click the subject title for more indepth information)
The old method of fusing stones made from chips and other unusable pieces of stone.
The bending of light passing through one medium to another, most often occurring with quartz.
A process developed by Willebrord Snell that incorporates a refractometer to measure the speed and angle of light as it enters a gemstone. It is used for critical gem identification.
In gemology, this refers to the raw, natural state in which gems are found.
A titanium dioxide mineral with needle-like inclusions (or foreign matter) within a stone. The rutile needles can be reddish (which is what rutile means in Latin). Often found embedded in quartz; can also produce some amazing gem phenomena as a star and a cat's eye in sapphire and other gems.
The same as above (rutiles), describes the type of specimen inclusions.
A deposit of gems that has been worn away from its original site, usually by the effects of weather. An alluvial deposit is an example of a secondary deposit.
Originally formed of sediment, including shale and sandstone, composed of fragments of other rocks deposited after transportation from their original source. Including those formed by precipitation, or by the secretions of animals as in certain limestones.
Containing one or two of the qualities of a 'precious' gem - beauty, durability or rarity.
Another name for iridescence, usually found as silvery or golden in some obsidian specimens.
A man-made stone that, unlike a simulant, has the same chemical composition and crystal structure as its natural counterpart.
The degree to which light passes through a material.
Gems that display three different colors when viewed from different angles.
A man-made stone of three parts that includes a clear protective top layer fused together with a thinly sliced gem, a dark backing material and a clear or colored adhesive.
The simplest form of gem polishing, in which the rough mineral is put into a revolving barrel with progressively finer abrasives, until a fine polish is obtained.
Found in many countries around the world, with specimens from the United States, México, Iran and Afganistan being the most sought after in valuable. An isomorphous mineral with chalcosiderite. Generally cut as a cabochon gemstone but frequently faceted or engraved. Often has an attractive blue or sky-blue color of fine-quality.
In gemology this term is loosely used to describe long thin lines that occur on the surface of the gem. The black lines seen in turquoise or howlite are two example of these veins.
An open cavity in rocks, often lined with crystals.
Rock enclosed in volcanic magma.