Calcite with two-beam interference colors & native copper (late Mesoproterozoic mineralization age, 1.05-1.06 Ga; Upper Peninsula of Michigan, USA) 5 : 無料・フリー素材/写真
Calcite with two-beam interference colors & native copper (late Mesoproterozoic mineralization age, 1.05-1.06 Ga; Upper Peninsula of Michigan, USA) 5 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
|---|---|
| 説明 | Large calcite crystal with two-beam interference colors & native copper from the Precambrian of northern Michigan, USA.The bedrock in northern Michigan's Keweenaw Peninsula area has Earth's highest concentration of elemental copper (Cu) in its native state. The copper has been extensively mined, but only one active mine remains (all the easily exploited copper is now mined out). Copper usually occurs in various late Mesoproterozoic-aged basaltic rocks and conglomerates.A beautiful and rare occurrence for native copper in northern Michigan is WITHIN crystals of calcite. This is a transparent to translucent calcite crystal that easily shows the metallic orange coloration of the included native copper. In the specimen shown above, the greenish-gray material at the periphery is weathered native copper.The rainbow-iridescence seen here is the result of two-beam interference. The colors are emanating from internal cleavage planes. Light that passes through the translucent calcite will get partially reflected back to the viewer by each cleavage plane. Partial light reflection occurs on both sides of the cleavage plane. The light reflecting from the back side of the plane will travel slightly farther to the viewer than light reflecting from the front side. The two beams of light interfere with each other, resulting in rainbow colors.I've observed this phenomenon in some calcite, fluorite, quartz, opal, and obsidian specimens.Stratigraphy & age: derived from the upper Portage Lake Volcanic Series, upper Mesoproterozoic (1.093 Ga); copper & calcite mineralization age is late Mesoproterozoic (1.05 to 1.06 Ga).Locality: unrecorded/undisclosed site in the Keweenaw Peninsula (very likely a copper mine), northwestern Upper Peninsula of Michigan, USA |
| 撮影日 | 2018-05-05 11:27:37 |
| 撮影者 | James St. John |
| タグ | |
| 撮影地 |