• Drusy gems form in a variety of ways, including igneous conditions.Don Smith/Photodisc/Getty Images
  
  A druse is the term used for a mineral formation. Specifically, a druse is a mineral that formed with a lot of small crystals across a surface. When a mineral forms this way it is called drusy.
  
  This kind of formation happens to various crystals. Some of the more commonly known minerals that form druses include pyrite, malachite, hematite, and carnelian as well as the somewhat lesser known uvarovite.
  
  

Pyrite

• Also known as fool's gold, pyrite (chemical formula FeS2) is a brass-colored iron sulfide used as a source for both iron and sulfur. The crystal system that pyrite belongs to is the cubic system. The name pyrite comes from the Greek meaning "in fire" or "of fire". It can be found all over the world.
  
  

Malachite

• Malachite is a copper carbonate (chemical formula Cu2CO3(OH)2) used as a gem and as a source of copper. It is green in color and belongs to the monoclinic crystal system. The name malachite comes ultimately from Greek, meaning "mallow-green stone". Malachite can be found in Egypt, France, Namibia, Arizona, the Ural Mountains, the Congo and Zaire.
  
  

Hematite

• Hematite or haematite (from the Greek "bloodlike stone") is an iron oxide (chemical formula Fe2O3). It belongs to the trigonal crystal system, forming in a variety of ways, and can be black, dark grey to silver grey or red, red-brown to brown in color. It is used as a source of iron, and places of note for hematite include Brazil, Australia, England, Canada, Mexico and the United States.
  
  

Carnelian

• Carnelian (also known as cornelian) is a form of quartz (chemical formula SiO2) with iron oxide (hemattite) impurities mixed into it during its formation. It is translucent, belongs to the trigonal system (like hematite), and possesses a red-brown to red color, due to the iron oxide. It is used in jewelry, and can be found in such places as India, Brazil and Australia.
  
  

Uvarovite

• Uvarovite (chemical formula Ca3Cr2(SiO4)3) is a variety of garnet that is consistently green, of an emerald shade. It is used in jewelry and is collected. It can be found, in connection with chromium ores, in such places as Russia, Canada (in Quebec) and Spain, and can also be found in South Africa, Finland and Norway.