An opening driven horizontally into the side of a mountain or hill for providing access to a mineral deposit. Strictly speaking, an adit is open to the atmosphere at one end, a tunnel at both ends.

 

A mineral occurring in small amounts, in addition to the primary mineral on a specimen.

 

The rarer of the two main types of stony meteorite, accounting for about 9% of all meteorite falls. Achondrites are made of rock that has crystallized from a molten state. They contain mostly one or more of the minerals plagioclase, pyroxene, and olivine, and generally, but not always, lack the small rounded inclusions known as chondrules that are typical of chondrites.

 

An aggregate of long, slender crystals shaped like needles.

 

Having a diamond-like luster. The brightest luster in minerals.

 

Displaying an exceptionally attractive form.

 

A group of crystals of one or more mineral types clustered together in a dense mass.

 

Any physical or chemical change in a rock or mineral subsequent to its formation. Milder and more localized than meta morphism.

 

Ammonites are mollusks, just like squids and octopuses. They are know to have existed from the Devonian Period of the Paleozoic Era, roughly 355 to 410 million years ago. They became extinct at the end of Cretaceous Period of the Mesozoic Era. So far, nearly 10,000 types of ammonites are known to us. Ammonites are used as index fossils (used to indicate the age of a stratum) and therefore considered a vital group for the study of the evolution of life.

 

A term applied to rocks or minerals that possess no definite crystal structure or form, such as amorphous carbon.

 

A small gas bubble in igneous, especially volcanic, rock filled or lined with secondary minerals and / or crystals.

 

Showing no typical crystal form or crystal faces.

 

Any departure from the norm which may indicate the presence of mineralization in the underlying bedrock. In geophysics and geochemistry, an area where the property being measured is significantly higher or lower than the larger, surrounding area.

 

A hard, black coal containing a high percentage of fixed carbon and a low percentage of volatile matter.

 

The top or terminal edge of a vein on surface or its nearest point to the surface.

 

Clusters that bear a structural resemblance to the branching growth qualities of trees.

 

Minerals containing the arsenate (AsO₄) radical as a major component.

 

The relative weight of an atom of an element as compared to the most stable isotope of carbon (At. Wt. 12.01115).