To turn on the AutoRecover feature: 1  In Word 2010, from the menu, select 2  . In the window that opens, click the tab, icon, or list item. 3  If it is unchecked, check , and type a value next to minutes. 4  Click to make the change.
What is tooth enamel? Tooth enamel is a hard substance found in the shell of each of your teeth and is the part of the tooth thatâs visible when you look in your mouth. Enamel is considered the hardest substance in the human body. Itâs even harder than your bones; however, it can dissolve or decay when exposed to acid and a build-up of bacteria.
Best Answer: Well, the hardest mineral on earth is a diamond. For rocks, which are made up of one or more minerals, the hardest are those which contain quartz. There is no single hardest rock but some of the rocks that would be very hard and strong and well-cemented quartz sandstones (a sedimentary rock), quartzite (a metamorphic rock formed from quartz sandstone) and granites or rhyolites (both igneous rocks with a lot of quartz).