Hyalite is a type of Opal sometimes known as Water Opal due to its high water content (between 3-8%). It is colourless but good crystals can fluoresce bright green under UV light due to the presence of uranium impurities. It was named in 1794 after the Greek word for 'glass', in reference to its appearance - in fact faceted Hyalite can often be indistinguishable from glass in appearance due to its purity.
| Alternative Names | Hyalite Opal, Mullers Glass, Water Opal |
| Colour | Green, White, Yellow |
| Hardness | 5.5 - 6.5 |
| Crystal system | Amorphous |
| Streak | White |
| Lustre | Vitreous |
| Main Locations | Mexico, Namibia, USA |
| Chakra | Crown |
| Zodiac | Cancer |
| Numerology | Unknown |
| Planetary | Unknown |
| Element | Unknown |
