Glass

saf-ahyuh r

Glass has been used for thousands of years as a decoration. It is sometimes employed as a gemstone simulant, but is often appreciated entirely upon its own merits, especially when formed with a high level of artistry.

Glass Polished
Glass Classification
Common Name Glass
Species Glass
Glass Optical Properties
Transparency Transparent - Opaque
Dispersion Strength: Moderate if Contains Lead Value: 0.009
Refractive Index 1.470-1.700
Tolerance:can go OTL
Optic Character NA
Optic Sign NA
Polariscope Reaction Aggregate (AGG)
Fluorescence SWUV: Variable
LWUV: Variable
Pleochroism None
Glass Characteristic Physical Properties
Hardness 5-6
Specific Gravity 2.300-4.500
Toughness Poor
Inclusions Since glass has a low mohs hardness and is usually molded the stones will have mold marks, rounded facet edges, concave facets. It will also sometimes show orange peel effect or a bumpy surface that resembles an orange peel. Glass will often show cavities on the surface of the stone and swirl lines and glass bubbles internally.
Luster Vitreous
Fracture Conchoidal, Granular, Splintery
Cleavage None
Glass Chemistry & Crystallography
Chemical Name silica
Crystal System NA

Glass Colors

  • Green Glass Green
  • Yellow Glass Yellow
  • White Glass White
  • Purple Glass Purple
  • Orange Glass Orange
  • Multi-color Glass Multi-color
  • Gray Glass Gray
  • Colorless Glass Colorless
  • Brown Glass Brown
  • Black Glass Black
  • Bi-color Glass Bi-color
  • Red Glass Red
  • Pink Glass Pink
  • Blue Glass Blue

Glass Spectra

Glass Spectra
GLASS

Color due to colloidal gold. A weak broad band in the green

Glass Spectra
GLASS

Color due to colloidal gold and rare earth elements. Early 20th.century costume Jewellry such as this bird brooch by Triffari and Co. used a "Ruby glass" in which the spectrum shows a marked separation between the rare earth lines and a narrower absorption band in the green. This results in a slightly paler version of " Ruby Glass" as an imitation ruby

Glass Spectra
GLASS

Color due to selenium. The strength and width of the broad band in the green indicates the amount of selenium present and may extend well into the blue-violet area in deeper brownish red colored glass.

Glass Spectra
GLASS

Color due to selenium. Total absorption up to 650nm

Glass Spectra
GLASS

Color due to colloidal gold. A single absorption band in the green centered at about 445nm. It may be accompanied by a series of other lines close by in yellow orange, due to rare earth elements

Glass Spectra
GLASS

Color due to colloidal gold. The single broad band in the green area centered at 550nm. results in a color representing a good imitation ruby often referred to as "Ruby glass" This can sometimes be accompanied by several lines close by on the long wave side due to rare earths.

Glass Spectra
GLASS

Color due to rare earth element. The dominant line is in the green at 520nm. With two other faint lines at 533nm. And 544nm. A broad but vague line at 489nm. Is accompanied by three finer weak lines at 458nm. 452nm. and 443nm. There is also a group of three faint narrow lines in the red between 650nm. and 660nm.

Glass Spectra
GLASS

Color due to rare earths, possibly neodymium A typical rare earth spectrum with a fine line at 610nm. followed by a group of lines in the yellow, the strongest at 584nm. and 570nm. A broad absorption centered at 429nm. consists of four weak lines in the green which are resolved when the spectrum is viewed through the pale colored ends of this stone. A strong line at 430nm. is closely followed by total absorption

Glass Spectra
GLASS

Color due to neodymium.  As is often the case the rare earth neodymium is responsible for the strong pink color in this glass. The broad absorption band in the yellow acts as a barrier to diminish the intensity of the light.

Glass Spectra
GLASS Blue

Color due to cobalt. A blue glass here shows a moderately distinctive three band cobalt spectrum. These are centered at 535nm. In the green 590mn. in the yellow and 655nm. in the red, Due to the pale blue color of this specimen these bands are relatively weak but are seen as individual bands. Note that the band in the yellow is narrower than the other two.

Glass Spectra
GLASS Blue

Color due to cobalt With high cobalt content the color saturation of blue glass increases and the absorption bands darken and widen. In deeper colored stones these bands may merge closer together. In some stones the bands at 590nm. And 655nm. appear as one broad band.

Jewelry Television acknowledges the significant scientific contributions of John S Harris, FGA to the study of gemstone spectra and with deep appreciation to him, acknowledges the use of his images and related notes about gemstones and their spectra in the educational materials on this website.

Alternate Names

Paste, Strass, Faience

Countries of Origin

Niger (the); Papua New Guinea; Cambodia; Gambia (the); Kazakhstan; Paraguay; Solomon Islands; Montserrat; Unknown; Mali; Guadeloupe; Panama; Bonaire, Sint Eustatius and Saba; Argentina; Seychelles; Belize; Zambia; Bahrain; Guinea-Bissau; Saint Barthelemy; Namibia; Finland; Georgia; Yemen; Tanzania, United Republic Of; Eritrea; Puerto Rico; Viet Nam; Aruba; Madagascar; Libya; Sweden; Malawi; Andorra; Saint Helena, Ascension and Tristan da Cunha; Liechtenstein; Russian Federation (the); Poland; Bulgaria; Jordan; United States Minor Outlying Islands (the); Tunisia; Tuvalu; Kenya; French Polynesia; Djibouti; Lebanon; Azerbaijan; Cuba; Mauritania; Saint Lucia; Guernsey; Congo (the Democratic Republic of the); Mayotte; Israel; San Marino; Australia; Tajikistan; Myanmar; Cameroon; Gibraltar; Cyprus; Malaysia; Iceland; Oman; Bosnia And Herzegovina; Armenia; Gabon; Korea (the Republic of); Luxembourg; Brazil; Algeria; Cabo Verde; Jersey; Slovenia; Colombia; Ecuador; Iran (Islamic Republic of); United States of America (the); Vanuatu; Honduras; Italy; Antarctica; Turks and Caicos Islands (the); Nauru; Haiti; Afghanistan; Burundi; British Indian Ocean Territory (the); Singapore; French Guiana; American Samoa; Christmas Island; China; Martinique; Sudan (the); Kyrgyzstan; Comoros (the); United Kingdom of Great Britain and Northern Ireland (the); Reunion; Saint Pierre And Miquelon; Cote D'Ivoire; Bhutan; Multiple; Romania; Togo; Cocos (Keeling) Islands (the); Dominican Republic (the); Uzbekistan; Holy See (the); Netherlands (the); Pitcairn; Zimbabwe; Montenegro; Dominica; Indonesia; Benin; Angola; Virgin Islands (British); Brunei Darussalam; Portugal; New Caledonia; Grenada; Moldova (the Republic of); Greece; Latvia; Mongolia; Morocco; Guatemala; Guyana; Iraq; Chile; Nepal; Cayman Islands (the); Isle of Man; Ukraine; Ghana; Anguilla; Saint Vincent And The Grenadines; India; Canada; Maldives; Turkey; Belgium; Faroe Islands (the); South Africa; Bermuda; Aland Islands; Jamaica; Peru; Turkmenistan; Venezuela (Bolivarian Republic of); Germany; United Arab Emirates (the); Fiji; Tokelau; Hong Kong; Guinea; Chad; Somalia; Thailand; Cook Islands (the); Equatorial Guinea; Kiribati; Costa Rica; Saint Martin (French part); Kuwait; Nigeria; Central African Republic (the); Palestine, State of; Croatia; Sao Tome And Principe; Syrian Arab Republic; Sri Lanka; Uruguay; Timor-Leste; Switzerland; Samoa; Spain; Liberia; Burkina Faso; Swaziland; Lao People's Democratic Republic (the); Palau; Estonia; Wallis and Futuna; Niue; Svalbard And Jan Mayen; Austria; Mozambique; El Salvador; Monaco; Guam; Lesotho; Tonga; Heard Island And Mcdonald Islands; Western Sahara; Hungary; Republic of Kosovo; South Sudan; Congo (the); Japan; Belarus; Curacao; Mauritius; Taiwan (Province of China); Bouvet Island; Albania; Bolivia (Plurinational State of); Norfolk Island; Trinidad And Tobago; Virgin Islands (U.S.); New Zealand; Sint Maarten (Dutch part); Senegal; Micronesia (Federated States of); Ethiopia; Macedonia (the former Yugoslav Republic of); Czechia; Egypt; Falkland Islands (the) [Malvinas]; Marshall Islands (the); Sierra Leone; Malta; Saudi Arabia; South Georgia And The South Sandwich Islands; Pakistan; Ireland; Qatar; Slovakia; France; Lithuania; Serbia; Bahamas (the); French Southern Territories (the); Rwanda; Saint Kitts And Nevis; Bangladesh; Barbados; Nicaragua; Norway; Botswana; Macao; Denmark; Mexico; Northern Mariana Islands (the); Uganda; Suriname; Philippines (the); Greenland; Antigua And Barbuda

History

Although glass isn't, technically, a gemstone, it's used so often as a simulant and in beads we feel it's worthy of listing. Most glass is man-made and has a hardness of 5 - 51/2 on the Mohs scale. It's made from sand that is almost pure silicon dioxide, with a few proprietary additives to adapt for temperature and color. Glass is a go-to product for jewelry due to its versatility. It can be colored, twisted, textured, sand-blasted, bent and even faceted. In short, glass is limited in design only by the imagination. It can simulate most gemstones. The downside? Glass is fragile and can be worn away over time. It's best suited for necklaces and earrings. If your bracelets and rings are made of glass, exercise care when you wear them. Glass pieces should always be stored in a well-protected space.

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Optical Phenomena

Color Change

This man-made jewel is unique in that is displays the optical phenomenon of color change. Although this is not a natural phenomenon, it is an affordable alternative to rare and expensive color change gems, such as alexandrite. You can observe color change in this jewel by viewing it interchangeably in natural and incandescent light.

Color Change Glass
Color Change Classification
Common Name Color Change
Color Change Characteristic Physical properties
Inclusions Color change glass can have mold marks, concave facets, rounded facet edges and display the orange peel effect. Glass stones often have gas bubbles, flow lines and they might show cavities on the surface.

Cat's Eye

The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case man-made glass. The effect, when present, appears as a bright, narrow slit similar to the pupils in the eyes of your favorite feline. This phenomenon is caused by parallel fibrous or needle-like inclusions that interfere with the passage of light through the crystal, scattering and reflecting light back to the viewer as a thin line.Although in this case the phenomenon is not natural, it offers an affordable alternative to this rare phenomenon seen with some natural gems.

Cat's Eye Glass
Cat's Eye Classification
Common Name Cat's Eye
Cat's Eye Optical Properties
Refractive Index 1.47-1.70
Cat's Eye Characteristic Physical properties
Inclusions Cat's-eye glass will have a honeycomb structure when viewed from the side if the cabochon. Stones might have gas bubbles, swirl marks, flow lines or a reflective base.
Tim Matthews

Author

Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.