Qandilite
Chemical formula: (Mg,Fe<sup>3+</sup>)<sub>2</sub>(Ti<sup>4+</sup>,Fe<sup>3+</sup>,Al)O<sub>4</sub>
Qandilite is a rare, black mineral of the spinel group, an oxide of magnesium and titanium, found mainly in metamorphic rocks.
Properties
- Mohs hardness
- 6.5
- Luster
- Metallic
- Streak
- Black
- Density
- 3.96
- Cleavage
- None
- Fracture
- Conchoidal
- Transparency
- Opaque
- Crystal system
- Cubic
Diagnostic features
## Identification Qandilite is identified by its black color, metallic luster, and occurrence as small, usually octahedral crystals or grains in skarns or kimberlites. It is hard (does not scratch steel) and shows no magnetism. ## Distinguishing from Similar Minerals It can be confused with other black spinels, such as magnetite, hercynite, or chromite, as well as with ilmenite. It is distinguished from magnetite by the absence of magnetic properties. Final and certain differentiation from other visually similar minerals requires advanced analytical methods, such as X-ray microanalysis (EDS/WDS). ## Crystal Forms It most often forms small, isometric crystals with an octahedral habit, often with rounded edges. It also occurs as irregular, anhedral grains embedded in the rock.
Geological environment
## Genesis Qandilite forms under conditions of high-temperature contact metamorphism. It typically forms in skarns created at the contact of magmatic intrusions with carbonate rocks (limestones, dolomites). It is also found as an accessory mineral in kimberlites. ## Mineral Associations It most commonly coexists with forsterite, calcite, spinel (sensu stricto), perovskite, geikielite, and magnetite. ## Localities The main confirmed localities for this mineral are the Qandil mountain range in Iraq (type locality), the Haystack Butte kimberlite deposit in Wyoming (USA), the Koidu complex in Sierra Leone, and some occurrences on the Siberian platform in Russia.
Rarity
Very rare
For collectors
## Quality Criteria For qandilite, the main criterion of value is the mere presence of a confirmed mineral in the collection. Specimens with well-formed, sharp-edged crystals are most prized, which is extremely rare. The abundance of occurrence on the matrix and the analytically confirmed identity of the mineral are also important. ## Popular Localities Specimens from the type locality in Iraq are historically most significant, although extremely difficult to obtain. Material for research and collections also comes from kimberlites in the USA and Sierra Leone.
Care and storage
## Cleaning Qandilite specimens, usually inclusions in the host rock, can be cleaned with a soft brush using distilled water. Strong scrubbing should be avoided to prevent damage to the matrix. ## What to Avoid The mineral is chemically stable, but contact with strong acids should be avoided. Ultrasonic cleaners are not recommended, as they could cause small crystals to detach from the rock. It is resistant to light and normal temperature changes. ## Storage Qandilite should be stored in stable conditions, away from dust. It is best kept in a closed display box with a label containing location data.