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Tips (Glossary of Terms)
| Magma |
| Rock in a molten state below the earth?s surface. |
| Intrusive |
| Igneous rock that has solidified within other rocks, below the Earth?s surface. |
| Centrifugal Casting |
| A casting technique whereby molten metal is thrust into a mold by centrifugal force. The most common method is by means of a spring driven arm supporting a crucible and a mold flask. |
| Matrix |
| The rock in which a gem is found. Also known as host rock or parent rock. |
| Refraction |
| Bending of light as it passes from air into a different medium. |
| Associated Minerals |
| Minerals found growing together, though not necessarily intergrown. |
| Burr |
| A rotary steel cutting tool used in a flexible shaft machine. |
| Binding Wire |
| Soft iron used to hold joints and pieces of metal in the desired position while being soldered. |
| Crucible |
| A ceramic or graphite container in which metal is melted. |
| Iridescence |
| Reflection of light off internal features in a gem, giving rise to a rainbow like play of colors. |
| Mammillated |
| Smooth rounded shape. |
| Cameo |
| Design in low relief, around which the background has been cut away. The result is a design that protrudes from the base of the stone. |
| Diffraction |
| The splitting of white light into its constituent spectral colors - the colors of the rainbow - when it passes through a hole or grating. |
| Basal Pinacoid |
| Feature relating to crystal symmetry. A columnar or prismatic crystal with flat ends may be referred to as having a basal pinacoid. |
| Placer Deposit |
| Concentrated (secondary) deposit of minerals, usually in rivers or seas. |
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