In detecting nicotine and its metabolites in the body, levels remain detectable in the urine only for 3 to 4 days. However, this may be different for some cases. For passive smokers, urine nicotine test can be positive for as long as 15 to 20 days.
This slate blends well with any type of stone or frame structure and is also used as the basic percentage, usually 50%, in roofs where several colors are mixed. Semi-Weathering Gray - A traditional slate-gray color ranging from a clear appearance to having small black markings.
Jeffrey S. Levine. Slate is one of the most aesthetically pleasing and durable of all roofing materials. It is indicative at once of the awesome powers of nature which have formed it and the expertise and skill of the craftsman in handshaping and laying it on the roof.