Prehnite 4mm Faceted Bicone - 15-16 Inch Dendritic Opal It is a rare occurrence

It is a rare occurrence to find gem-grade hackmanite

Agate has been discovered with artifacts from cultures of the Neolithic Period

it has often been used as a substitute

These flecks glitter as they catch the light and appear green against the dark glass

a silicate of calcium and magnesium -- from western Canada

Prehnite 4mm Faceted Bicone - 15-16 Inch Dendritic Opal It is a rare occurrencePrehnite was the first mineral to be named after a person: its discoverer, Dutch Colonel Hendrik Von Prehn. Von Prehn discovered the stone in South Africa in 1774. Prehnite is translucent to transparent, in colors from light green to yellow green to olive, with occasional inclusions of Black Tourmaline that crisscross the stone in fibrous patterns. It is a phyllosilicate composed of silicon, calcium and aluminum with trace amounts of iron.