Sodalite and Lapis Lazuli can look quite similar and it is one that I see a lot of confusion over. The following are a few tips on how to identify which you have. The video offers information as well as shows you a side by side comparison.
Lapis Lazuli: 5-5.5
Lapis Lazuli: Blue
Colors and Mineral Content:
Sodalite: Sodalite has the chemical composition of Na8Al6Si6O24(Cl2,S) (Sodium aluminum silicate with chlorine, and occasionally sulfur). It is a Feldspathoid, which is a aluminosilicate mineral that contains abundant calcium, potassium, or sodium and too little silica to form feldspar. However, feldspathoids do commonly occur with feldspars. Sometimes Sodalite will have a dark gray to black mineral inclusion that can product chatoyance. My research has lead me to believe that mineral is Nepheline Syenite, but I am not positive. If anyone knows for sure, please do let me know. (Click here to read more about Sodalite.)
Lapis Lazuli: Lapis Lazuli has the chemical composition of (Na,Ca)8Al6Si6O24(S,SO)4 (Sodium, Calcium, Aluminum, Silicon, Oxygen). Lapis Lazuli is not a mineral. It is a rock composed of multiple minerals. The primary mineral is Lazurite, which gives Lapis its blue color. The other two most common mineral inclusions are White Calcite and Pyrite. Pyrite is not always included in Lapis Lazuli, so using this as your definitive way of telling Lapis Lazuli from Sodalite is not recommended. White Calcite is the second most common mineral inclusion in Lapis Lazuli. “Its presence can be very obvious, appearing as white layers, fractures, or mottling. It can also be finely intermixed with Lazurite to produce a rock with a faded denim color.” (geology.com) (Click here to read more about Lapis Lazuli.)
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