Slate can also contain abundant quartz and small amounts of feldspar, calcite, pyrite, hematite and other minerals. Most slates are gray in color and range in a continuum of shades from light to dark gray. Slate also occurs in shades of green, red, black, purple and brown.The color of slate is often determined by the amount and type of iron and organic material that are present in the rock.The tectonic environment for producing slate is usually a former sedimentary basin that becomes involved in a convergent plate boundary.he color of slate is often determined by the amount and type of iron and organic material that are present in the rock. The tectonic environment for producing slate is usually a former sedimentary basin that becomes involved in a convergent plate boundary.
How wearing contact lenses all day can DESTROY your eyesight: Read one woman's cautionary tale. 1  Fashion designer Aimee McWilliams, 33, from London wore contacts daily. 2  Up to 8 hours wear a day is recommended but she wore them for 14.
The lifespan of a closure depends on the quality of the hair and the cap construction. Well constructed closures can last as long as 3-5 years. Others have a lifespan of 3-12 months. Again the lifespan depends on many factors that contribute to the wear factor. (care, quality, etc..) Due to the delicate nature of the materials in which it is constructed from, lacefrontals may have a lifespan of 3-12 months depending on a variety of factors that contribute to the wear factor.