The calcite crystals in the Keokuk geodes are truly amazing. I will try to show you, with the help of my wife the photographer, the many crystal forms present. Sorry about the big words.
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Pink calcite on quartz: Scalenohedron calcite with rhombohedral terminations. These are the Cadillac of Keokuk geode calcite. Nice pink 'phantoms' within big clear/milky crystals. The pink scalenohedron was the first to crystallize, followed by clear/milky crystals in a later period of mineralization. The finest were found at the 'old' St Francisville mine in Missouri.
Pink calcite on quartz: Closeup of previous geode. Rumor has it that a ten inch dewdrop diamond geode was found at this mine containing these pink calcites. If this is true and you have it... Mercy day.
Calcite on quartz: Hexagonal prismatic barrel calcite with rhombohedral terminations. Geode from the 'new' mine in St Francisville (Alvis mine). This mine is legendary for its big calcite crystals.
Calcite on blue chalcedony: Scalenohedron calcite with rhombohedral terminations on blue chalcedony lightly sprinkled with clear dewdrop diamonds.
Calcite on dolomite on quartz: Rhombohedron and pseudo-cubic rhombohedrons with penetration twins. Just say "angel wing" calcite, it is much easier.
Calcite and pyrite on quartz: Pretty "angel wing" calcite "flower" with a pyrite crystal aesthetically placed by the geode angel.
Calcite and pyrite on blue chalcedony: Negative rhombohedron. This is called "nailhead" calcite.
Calcite on quartz: "Nailhead" calcite crystal on a bed of calcite.
Pink calcite - Scalenohedron: This is called "dogtooth" calcite. The interior of this pink calcite geode has absorbed the iron mineral hemitite giving it a red color.
Brown calcite double geode: The other half of the previous geode has a twin... A brown calcite with secondary white calcite. These two geodes are stuck together, but they are very different in color and composition. Don't ask me.
Pink calcite on brown calcite: Clear "nailhead" crystals covering a pink "dogtooth" calcite crystal. This is called a 'pagoda.'
Pink calcite on blue chalcedony: Silky "pagodas."
Pink calcite on blue chalcedony: "Nailheads" stacked on a pink 'dogtooth.'
Pink calcite on brown calcite: The big brown calcite cube in the foreground caused a bit of confusion, in that it looked like the mineral fluorite. No fluorite in the Keokuks. The iridescence on the pink calcite is the mineral stilpnosiderite.
"Barrel" calcite on blue chalcedony: A beautiful cluster of clear rhombohedral calcite on top of a pink calcite crystal.
Brown "sugar" calcite: I call this type of geode "brown sugar". These are found at all brown calcite locations. The calcite crystals have a silky, sparkly, "sugar" coating that the camera cannot pick up. A really pretty geode that must be seen in person.
Included calcite: Marcasite included in calcite. Lots of cool minerals form inside and through the calcite crystals.
Included calcite: Milky calcite with included brown calcite crystals. The geode angel stuck a "fishtail" selenite crystal on this quartz/calcite formation.
Included calcite: Pyrolusite included calcite on quartz. Sometimes black spots show up in calcite and "new mineral" is hollered. Its most likely pyrolusite.
Three-dimensional calcite: Pretty calcite "flower" on gray chalcedony.
Smokestack calcite: Calcite and dolomite on quartz.
Calcite angel: Calcite and quartz. The angel is in there...somewhere.
Thumbnail Calcite: A perfect rhombohedron calcite crystal on dolomite and quartz in this one inch geode.
Thanks for look'n.