Diamond (gemstone) be considered appropriate for use as a gemstone; the other 80% are relegated to industrial use. Of that top 20%, a significant portion contains one or more visible inclusions. Those that do not have a visible inclusion are known as "eye-clean" and are preferred by most buyers, although visible inclusions can sometimes be hidden under the setting in a piece of jewelry. Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity. When set in jewelry, it may also be possible to hide certain inclusion behind mounting hardware such as prongs in a way that
Fishguard Volcanic Group recognised within the Strumble Head area. It is composed of acid tuffs. Fishguard Volcanic Group The Fishguard Volcanic Group is an Ordovician lithostratigraphic group (a sequence of rock strata) in west Wales. The name is derived from the town of Fishguard in Pembrokeshire. This assemblage of rocks has also been referred to as the Fishguard Volcanic Series or Fishguard Volcanic Complex. These rocks are believed to be the source of the 'bluestones' which form a part of the well-known prehistoric monument of Stonehenge in southern England. The rocks are intermittently exposed in a belt of country running east from Strumble