Manganotantalite with Apatite Included in Aquamarine

Manganotantalite
Manganese Tantalum Oxide, Mn++Ta2O6
Crystal System: Orthorhombic
Hardness: 6.0-6.5
Density: 8.00

Manganotantalite exhibits brownish-black crystals with reddish internal reflections. It occurs in granite pegmatites and is commonly associated with albite, microcline, and lepidolite. This specimen occurs with albite, aquamarine beryl and a tiny terminated bluish green apatite crystal. Occurrences of manganotantalite are reported at Taos City, New Mexico; Newry, Maine; Crystal Peak, Colorado; Walden, Connecticut and Minas Gerais, Gilgit, Pakistan.

Apatite
Calcium Phosphate Fluoride Hydroxide Chloride, Ca5(PO4)3(F,OH, Cl)
Crystal System: Hexagonal
Hardness: 5.0
Density: 3.16-3.22

Apatite is a group name, applied to phosphates, arsenates and vanadates. It's members are the most common of the phosphorus-bearing minerals. The group members are differentiated on the basis of their predominant anions i.e.: fluorapatite (FL), hydroxylapatite (OH), or chloroapatite (CL). Apatites are formed under a variety of conditions but most commonly occur as accessory minerals in igneous rocks. They also occur in marine sedimentary rocks formed by chemical deposition, in fossils, and in metamorphic rocks.

Apatites vary widely in color from colorless to yellow, green, brown, red and blue. Some apatites display a yellow fluorescence under ultraviolet light. Group members exhibit hexagonal, prismatic crystals which may be stubby to elongated and are often terminated by dipyramidal faces.

Beryl
Beryllium Aluminum Silicate Be3Al2SiO3
Crystal System: Hexagonal
Hardness: 7.5-8.0
Density: 2.65-2.90

Beryl is an important ore mineral of beryllium. It is typically found in cavities in granite and pegmatite and is also associated with tin ores and mica schists.

Bluish beryls are known as aquamarines. Other beryls are emerald (green), morganite (pink), and beryls that are red, brown, yellow, and pale green. The variations in color exhibited by beryls are probably due to small included quantities of different metallic oxides.


Rocks from Martin Friedlander's Collection

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bkeller@rockhounds.com 8/8/95