PaleoWilliam Posted June 22, 2016 Share Posted June 22, 2016 I need help on these. Link to comment Share on other sites More sharing options...
DPS Ammonite Posted June 22, 2016 Share Posted June 22, 2016 (edited) They look like calcite and aragonite on the inside of a concretion similar to the ones in the Britton Fm. in North Texas. They should fizz in vinegar and acid. They also might be fluorescent in a black light. Another test for calcite besides the acid test is a hardness test. See if an older penny (1980 or earlier) can scratch the crystals or if the crystals can scratch the penny. I'll bet the penny scratches the crystals since a penny is harder than calcite. Let us know what you find out. See Mohs hardness scale diagram to help you ID mineral hardnesses. Edited June 22, 2016 by DPS Ammonite 1 My goal is to leave no stone or fossil unturned. See my Arizona Paleontology Guide link The best single resource for Arizona paleontology anywhere. Link to comment Share on other sites More sharing options...
ynot Posted June 23, 2016 Share Posted June 23, 2016 I agree that it looks like calcite crystals on limestone. Tony Link to comment Share on other sites More sharing options...
Coco Posted June 23, 2016 Share Posted June 23, 2016 Hi, I think it is quartz because I can't see the plan of typical cleavage of the calcite... If it is the case, the vinegar will have no effect above. Coco ---------------------- OUTIL POUR MESURER VOS FOSSILES : ici Pareidolia : here Ma bibliothèque PDF 1 (Poissons et sélaciens récents & fossiles) : ici Ma bibliothèque PDF 2 (Animaux vivants - sans poissons ni sélaciens) : ici Mâchoires sélaciennes récentes : ici Hétérodontiques et sélaciens : ici Oeufs sélaciens récents : ici Otolithes de poissons récents ! ici Un Greg... Link to comment Share on other sites More sharing options...
ynot Posted June 23, 2016 Share Posted June 23, 2016 I would agree with Coco- there is a possibility that it could be quartz (agate)-- calcite and quartz crystals can have a very similar appearance that makes it difficult to tell which is in a picture. Either of the tests that have been requested will show the difference. Quartz = hard and no "fizz". Calcite = soft and "fizz". Tony Link to comment Share on other sites More sharing options...
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