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Shell

Shell

By Tim Matthews, JD, FGA, GG, DGA,
CEO and President of JTV (retired)
Published: June 2014
Modified: June 2023
Shell Polished Shell Jewelry
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Table of Contents
  • General Information
  • Shell Colors
  • Alternate Names
  • Countries of Origin
  • Care
  • Species/Variety

Most shells used in jewelry are the hard case of a mollusk. The best-known examples come from conchs, mollusks, black-lipped oysters, and abalone. Most shells are the byproduct of harvesting mollusks for food. Shell jewelry has been found from an archeological site in Morocco that dates to 82,000 years ago. Mother-of-pearl is used to decorate gun hilts and knife handles. Shell is a popular material with cameo carvers that take advantage of the colored banded layers to create dramatic scenes or human figures.

General Information

  • Classification
  • Optical Properties
  • Characteristic Physical Properties
  • Chemistry & Crystallography
Common Name
Shell
Species
Shell
Transparency
Translucent - Opaque
Refractive Index
1.530-1.685
Birefringence
0.155
Polariscope Reaction
Aggregate (AGG)
Hardness
3-4
Streak
White
Specific Gravity
2.700-2.890 Typical:2.860
Toughness
Poor
Inclusions
Fibrous growth structure.
Luster
Greasy, Pearly
Stability
Poor
Fracture
Uneven, splintery
Cleavage
None
Chemical Name
calcium carbonate, conchiolin and water
Chemical Formula
CaCO3 with H2O and other organic materials
Crystal System
NA
Chemistry Classification
Biogenic

Shell Colors

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

Alternate Names

Mother-of-Pearl

Countries of Origin

Papua New Guinea; Cambodia; Kazakhstan; Paraguay; Bahamas; Solomon Islands; Montserrat; Unknown; Mali; Marshall Islands; Guadeloupe; Panama; Bonaire, Sint Eustatius and Saba; Argentina; Seychelles; Belize; Zambia; Bahrain; Congo; Guinea-Bissau; Saint Barthelemy; Namibia; Comoros; Faroe Islands; Finland; Georgia; Yemen; Tanzania, United Republic Of; Eritrea; Puerto Rico; Viet Nam; Aruba; Madagascar; Libya; Sweden; Cocos (Keeling) Islands; Malawi; Andorra; Saint Helena, Ascension and Tristan da Cunha; Liechtenstein; Poland; Bulgaria; Jordan; Tunisia; Tuvalu; United Arab Emirates; 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; Northern Mariana Islands; Malaysia; Iceland; Oman; Bosnia And Herzegovina; Armenia; Gabon; Korea (the Republic of); Luxembourg; Brazil; Turks and Caicos Islands; Algeria; Cabo Verde; Jersey; Slovenia; Colombia; Ecuador; Iran (Islamic Republic of); Lao People's Democratic Republic; Vanuatu; United States Minor Outlying Islands; Honduras; Italy; Antarctica; Nauru; Haiti; Afghanistan; Burundi; Russian Federation; Singapore; French Guiana; American Samoa; Christmas Island; Netherlands; China; Martinique; Kyrgyzstan; Reunion; Saint Pierre And Miquelon; Cote D'Ivoire; Bhutan; Multiple; Romania; Falkland Islands [Malvinas]; Togo; Philippines; Uzbekistan; Pitcairn; Zimbabwe; British Indian Ocean Territory; Montenegro; Dominica; Indonesia; Benin; Angola; Virgin Islands (British); Sudan; Brunei Darussalam; Portugal; New Caledonia; Grenada; Moldova (the Republic of); Cayman Islands; Greece; Latvia; Mongolia; Morocco; Guatemala; Guyana; Iraq; Chile; Nepal; Isle of Man; Ukraine; Ghana; Holy See; Anguilla; Saint Vincent And The Grenadines; India; Canada; Maldives; Turkey; Belgium; South Africa; Bermuda; Aland Islands; Central African Republic; Jamaica; Peru; Turkmenistan; Venezuela (Bolivarian Republic of); Germany; Fiji; Tokelau; Hong Kong; Guinea; Chad; Somalia; Thailand; United Kingdom of Great Britain and Northern Ireland; Equatorial Guinea; Kiribati; Costa Rica; Saint Martin (French part); Kuwait; Nigeria; Palestine, State of; Croatia; Sao Tome And Principe; Syrian Arab Republic; Cook Islands; Sri Lanka; Uruguay; Timor-Leste; Switzerland; Samoa; Spain; Liberia; Burkina Faso; Swaziland; 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; 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; United States of America; Egypt; Sierra Leone; Malta; Saudi Arabia; South Georgia And The South Sandwich Islands; Pakistan; Gambia; Ireland; Qatar; Slovakia; France; Lithuania; Serbia; Niger; Rwanda; Saint Kitts And Nevis; French Southern Territories; Bangladesh; Barbados; Nicaragua; Norway; Botswana; Macao; Denmark; Dominican Republic; Mexico; Uganda; Suriname; Greenland; Antigua And Barbuda

Care

Soluble in hydrochloric acid. Shell is very soft, so be mindful of scratching. Avoid sudden temperature changes, chemicals, and ultrasonic cleaners. In addition to above precautions: avoid perfumes, and hairsprays.

Species/Variety

Tortoise Shell

Tortoise shell used in ornamentation traditionally comes from the shell of the hawksbill sea turtle. The multicolored marbled patterns of the shell are coveted not only for their unique colorations, but also their deep translucence. When heated, the shell becomes soft and can be molded into jewelry and other decorated articles. Due to the depletion of the species today, its use is illegal in many countries and has primarily been replaced by synthetic tortoise shell.

Tortoise Shell Shell
Tortoise Shell Shell
  • Classification
  • Characteristic Physical properties
Common Name
Tortoise Shell
Specific Gravity
1.26
Toughness
Fair
Inclusions
Tortoise shell will have mottled coloration, numerous spherical particles that give it a dot like pattern under magnification. Plastic imitations will have a swirl like pattern.

Quahog Shell

Quahog shell exhibits attractive purple and white bands when polished. Native Americans polished them into beads called wampum that they used for trade and decoration.

Quahog Shell Shell
Quahog Shell Shell
  • Classification
Common Name
Quahog Shell
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