Ammonite Douvilleiceras Polished 6.5cm Last Chance Mineraloids are substances that look Mineraloids are substances that look like minerals but do not display crystals (a key property of minerals): the unique formation process of Obsidian explains why it can be considered a mineraloid 3cm tall displays a stunning Quartz base adorned with beautiful circles and tube like banded patterns of translucent Blue Grey Chalcedony Agate as well as its impressive fern like suture patterns bacteria broke the ammonite body down and water started to dissolve the original ammonite shell (this shell was later replaced with minerals like Calcite)