La coquille flammée du casque rouge, Cypraecassis rufa

Jean-Pierre Gauthier (1), Jacques Fereire (1) & Thanh Nhan Bui (2) Abstract The flame structure of the red helmet shell, Cypraecassis rufa (Linnaeus, 1758) Among molluscs with so-called “porcelaneous” shells, consisting of non-nacreous aragonite, we chose a gastropod, Cypraecassis rufa, to show an example of flame structure on cabochon-cut samples. The crossed structure of this […]

Une remarquable tourmaline elbaïte non cuprifère

Franck Notari (1) (2), Féodor Blumentritt (2), Yolchanok Srinaka (1), Natthawut Saenkuntha (1) Abstract The popularity of Paraíba-type tourmalines is mainly due to their remarkable colour, often described as « neon » blue. Many tourmalines with this colour are traded under the label Paraíba, but sometimes mistakenly. Today, gemmological laboratories devote particular attention to the detection of […]

Kreuter (1842-1987), fabricant méconnu

Marie Chabrol (1) & Charline Coupeau (2) Abstract The city of Hanau in Germany was one of the most important jewelry production centers of Europe between the end of the 19th century and the beginning of the 20th. It’s in this city that the Kreuter workshop was based, which ensured most of qualitative productions of […]

Les verres naturels

Ingrid Lerouyer (1) Abstract This article presents the main varieties of natural glasses and classifies them into three categories, each linked to their mode of formation. In the wild, glass can be found through volcanic, meteoritic impact or lightning-related events. At the end of this article, a table lists the characteristics and optical phenomena most […]

Revue sur les minéraux de qualité gemme du Canada.

Daphné Giacomazzi (1), Marianne Dragon (1), Marie-Hélène Corbin(1) Abstract Canada is a country rich in its diversity of minerals, some of which have gem varieties. Yet only three gemstones are of both local and international economic importance: the diamond, the nephrite jade and the ammolite. Other gems, such as hessonite garnet, are not abundant enough […]

Méthodes de calcul des formules structurales des gemmes

Marine Bouvier (1) Abstract This article aims to explain the content of the experimental dissertation prepared by Marine Bouvier (2023) for her university diploma in gemology (DUG, Nantes entitled “Calculation methods of structural formulas for gemstones”. The utilities and uses of the structural formulas are explained, along with the percentage of pure pole components of […]

Le chemin de la durabilité

Chloé Picard (1) ABSTRACT The adjective sustainable (“durable” in French) is, according to the French dictionary Petit Robert, “likely to last a long time”. Still according to this noble book, a company is defined as “an organization for the production of goods or services of a commercial nature”. To last, a company must, among other […]

Nouvelles considérations sur la sodalite-hackmanite de la région de Mogok, Myanmar

Emmanuel Fritsch1, Nicolas Hébert2, Feodor Blumentritt1,3, Cassandre Moinard1 ABSTRACT A parcel of 13 kg of hackmanite from the Mogok area, Myanmar triggered some surprising observations that contribute to the knowledge of hackmanite, the photochromic variety of sodalite. Firstly, we point out that nearly 350 samples reach exactly the same color saturation under UV-rich natural sunlight […]