Browse Items (264 total)

Taxonomy Phylum: Echinodermata Class: Crinoidea Diagnostic Features Crown Stalk Pentaradial symmetry Ossicles Calyx Pinnule Holdfast Way of life Benthic (some pseudoplanktonic) Filter feeders Stratigraphic range Ordovician to present Advanced…

Compare with microcrystalline.

Formula CaMg(CO3)2 Structure Non-silicate Crystal System Crystal system: trigonal (-) Physical Properties Colour in hand specimen: white, often tinged with yellow or brown Cleavage: rhombohedral Hardness: 3.5-4  Optical…

See: adamantine

Taxonomy Phylum: Echinodermata Class: Echinoidea Diagnostic features Ambulacra (tube feet) Periproct (opening for anus) Peristome (opening for mouth) Pentaradial symmetry (regular echinoids) Bilateral symmetry imposed upon pentaradial symmetry…

See aeolian.

Formula Ca2Al2O∙(Al,Fe3+)OH[Si2O7][SiO4] Structure Orthosilicate Crystal System Crystal system: monoclinic (-) Physical Properties Colour in hand specimen: greenCleavage: one, perfectHardness: 6 Optical Properties Colour in plane…

See: ultramafic cumulate (L171)