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.
On the data front, Verizon also keeps your IP session information for one year. T-Mobile does not keep this information, AT&T only retains non-public IPs for 72 hours, and Sprint keeps it for 60 days.Similar policies are in place for IP destination information, except for Verizon, which keeps the information for 90 days.all detail records, meanwhile, are retained for one year by Verizon, five years for T-Mobile (two years for pre-paid), five to seven years for AT&T, and 18 to 24 months for Sprint.