Silica minerals
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Glasgow Museums has a collection of over 1,200 silica mineral specimens. This collection mostly comprises quartz, with specimens ranging from individual crystals to large crystal groups. As well as quartz, the collection contains other varieties of silica showing a range of colours, including rock crystal (clear), amethyst (purple), smoky quartz or cairngorm (brown to grey), citrine (yellow) and rose quartz (pink). Among the specimens composed of microscopic crystals there are examples of chalcedony, agate, onyx and jasper. These specimens come from various parts of the world, including Scotland. Opal, a form of silica containing water, is represented by examples from Australia and a few other localities. Quartz is composed of silica or silicon dioxide. It occurs in many different colours and forms, and these different varieties have different names. Although quartz is the commonest of all minerals it can produce very attractive specimens and some varieties are considered to be semi-precious gemstones.
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