Comments on Beryl Colors and on Other Observations Regarding Iron-containing Beryls
Notice bibliographique
Résumé
Abstract Trivalent iron ions substituting for Al3+ are present in many beryls and are abundant in dark red and dark blue beryl. These ions do not contribute any color to the crystals. Dark blue beryl also contains octahedral Fe2+ ions, which are involved in giving the crystal the blue color. The colors of dark red and dark blue beryls are very stable. Tetrahedral iron ions are practically absent in these beryls, but are present in other beryls which change their color upon irradiation and heating. Their colors depend more on the radiation and temperature history of the crystals than on chemistry. Trivalent iron ions substituting for Si4+ also do not contribute color. Rare observations by EPR (electron paramagnetic resonance) indicate that the charge difference can be compensated either by protons or by alkali ions in the beryl channels. It is shown that about 1% of the Fe3+ ions in dark red beryl substitute for Si4+. The changing colors of iron-containing beryls have been interpreted in many different ways, but it is likely that they are due to ions substituting for Be2+. The present study suggests that the iron ions do not substitute isomorphically for Be, but that they enter a distorted tetrahedron which consists of one O(1) oxygen and three O(2) oxygens. The center of this T(3) tetrahedron is at (0.432, 0.344, 0.167) in the beryl structure and the distance to the four oxygen ions is 1.84 Å, compared to 1.65 Å in the Be tetrahedron, thus providing more space for the much larger iron ions. This site is so close to the Be site that both sites cannot be simultaneously occupied. Beryl crystals with Fe2+ ions in T(3) are colorless. Irradiation oxidizes these Fe2+ ions to Fe3+, which gives the beryl a yellow color. The aquamarine color is caused by pairs of Fe2+ and Fe3+ ions in neighboring T(3) tetrahedra. When both configurations are present, the crystal assumes a shade of green, depending on their relative proportion. The electrons released by the irradiation are trapped at sites which are probably associated with water molecules in the beryl channels. These electrons leave the traps upon heating and reduce the Fe3+ ions in the T(3) tetrahedra. The yellow color vanishes and the beryl becomes aquamarine blue. More electrons are released at higher temperatures and reduce both ions of the pairs, leaving the beryl colorless. The oxidation of the iron ions at even higher temperatures is connected with the release of water from the beryl crystal. A number of small EPR signals in addition to the large signal from octahedral Fe3+ ions in iron-containing beryl crystals are investigated. Many arise from exchanged-coupled Fe3+ ion pairs, and one is related to the yellow color.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».