Occasionally, when amethyst, chalcedony, garnet, or similar mineral crystals grow they can form a tightly-packed matrix which creates a dense bed of individual crystals, each with only a single termination pyramid exposed. When this bed of crystals has a very fine crystalline structure similar to sugar or salt crystals, it is known as "druzes," "druzy," "drusies," or "druzi," which is described as having an "encrustation" crystal habit. This aggregate of minute crystals coating a surface is also referred to as "druzy encrustation."
Orthoceras are a famous and very large fossil deposit of animals that can be found in Morocco, North Africa. Ancestors to ammonites, Orthoceras are extinct sea creatures, and depending on what source you refer to, they date from the lower Ordovician to Triassic ages (500 to 190 million years ago). As they died, their shells accumulated in great numbers on the sea floor where they were aligned by currents, buried by sediments, and transformed over the ages preserved in black limestone. Today, this prehistoric sea floor is ironically, found in the dramatic Atlas Mountain Range in southern Morocco at the northern fringe of the Sahara Desert.
Ammonites are perhaps the most widely known fossil, possessing the typically ribbed spiral-form shell as pictured above. These creatures lived in the seas between 240 - 65 million years ago, when they became extinct along with the dinosaurs. The name 'ammonite' (usually lower-case) originates from the Greek Ram-horned god called Ammon. Ammonites belong to a group of predators known as cephalopods, which includes their living relatives the octopus, squid, cuttlefish and nautilus.
