FMF - Friends of Minerals Forum, discussion and message board

[CornelDumitru]

Please help me identify the mineral composing the geodes.
The hardness is 3-4.
Taste is salty!
I can not see a reaction to LWUV.
The geodes are hosted in a block found on the shore of Lake Costinesti in Romania, close to the Black Sea shore. Suggesting Sarmatian Stage, salt water, evaporation, sedimentation.
The rock is, I would guess, mostly dolomite. It produces gas bubbles with vinegar, but in a calm reaction, not violently.
The crystals from geodes slowly dissolve in vinegar.
My first supposition was: halite geodes.
But the crystal habit, as I can show in photos attached (6-7 mm diagonal), does not look right for halite, to me.
So: celestite (celestine), halite, calcite, or what ?

[James Catmur]

Given the taste, halite seems likely. Could the crystals be partially dissolved in water?

[Bob Morgan]

The closeup shot 14-06-28 looks like a calcite crystal with the c-axis being where the bright spot is and the trigonal morphology around it.
Could the saltiness just be a coating from exposure to an external source of salt?

[CornelDumitru]

[Don Lapham]

Celestite contains Strontium which would burn with a red color in a flame. Calcite and Halite contain Calcium and Sodium, respectively, which both burn orange. If you can crush a tiny portion of the crystal into a powder and carefully sprinkle it into a flame (preferably in a dark space) you should be able to see the red color of Strontium if it is present.