Gemology Hub | Gemstone & Mineral Identification Guides

 Spodumene  spodumene pronunciation Spodumene, a member of the pyroxene group, is lithium aluminium silicate LiAlSi 2 O 6 and forms highly characteristic flattened and striated prismatic transparent crystals of the monoclinic system with good cleavages in two directions intersecting nearly at right angles and a notably brittle tendency. The hardness is 6.5–7 and the SG 3.18. The RI for the alpha, beta and gamma rays is 1.648–1.663, 1.655–1.669 and 1.662–1.679 respectively with biaxial positive DR 0.014–0.027. Crystals are strongly pleochroic with lilac, green or yellow in one direction and colourless in the other. The varieties include a yellow to pale green spodumene with no varietal name, the lilac-pink kunzite and a very rare chrome-green hiddenite. Kunzite shows no useful absorption in the visible but the chrome-green hiddenite shows a characteristic chromium spectrum with the customary strong doublet in...

Zircon   {Jargoon, Hyacinth, Jacinth} Note: Jargoon or jargon is a name applied by gemologists to those zircons which are fine enough to be cut as gemstones, but are not of the red color which characterizes the hyacinth or jacinth. While zircon in fashioned form can be found in a wide range of colours the crystals are usually reddish brown and heat treatment is needed to produce the colourless, golden yellow and bright blue colours most seen in jewellery. Other colours, often very pleasing, might be called fancy zircons as the range is considerable. We should understand from the first that some zircons are much older than others and, like older people, behave in different ways. Over time some zircons have suffered a break- down of their crystal lattice to the extent that in extreme cases they are to all intents and purposes amorphous. They show little or no birefringence and their physical properties are different from those of other zircons. They are ‘low’ zircons and co...