CALCITE ON BOTRYOIDAL CHALCEDONY, Kara Mine Tasmania

What initially looks like boring dull calcites actually is botryoidal chalcedony with an overgrow of calcite. So basically, Aussie Grape Agate. We have never seen this before from a Tasmanian location. 

The word "botryoidal" comes from the Greek term "botrys," which means "bunch of grapes." It refers to a unique way that some minerals form, where crystals create rounded, globular shapes instead of sharp, pointed ones. This type of formation can be found in minerals like hematite, malachite, and smithsonite, but botryoidal chalcedony is especially valued for its beautiful translucency and variety of colors. Chalcedony is a type of silica made up of tiny crystals of quartz and moganite. When it forms in these rounded shapes, it gives off a soft, natural look that is pleasing to both touch and sight.

Moganite is a type of tectosilicate mineral with the chemical formula SiO2, which means it is made of silicon dioxide. It was first discovered in 1976 in the Barranco de Medio Almud ravine located in Mogán, Gran Canaria, part of Spain's Canary Islands. Initially thought to be a new form of silica, it was named after its discovery site. However, in 1994, the International Mineralogical Association (IMA) decided that moganite was not a valid mineral because it looked too much like quartz. Later research led the IMA to change its mind in 1999, officially recognizing moganite as a distinct mineral species. Although it shares the same chemical makeup as quartz, moganite has a different crystal structure. This mineral is typically found in dry areas like Gran Canaria and Lake Magadi, and it has also been reported in various places across Europe, India, and the United States. Moganite has a Mohs hardness of about 6, a dull luster, and a semitransparent gray color.