The Vikings were renowned navigators at a time before magnetic compasses were invented. So how'd they manage it? Their secret may have been these pretty-pointed crystals of calcite called Iceland spar, and this month's SciShow Rocks...

Today on SciShow news, dead person wisdom is helping enrich our understanding of the natural world - how did Vikings manage to be such awesome navigators? And is heart disease inherent in human beings? Scientists think mummies may have...

From corundum to alexandrite, there are rare minerals have multi-colors caused by how they form their structure!<br/>