Homilite

Last updated
Homilite
General
Category Nesosilicate
Formula
(repeating unit)
Ca2(Fe2+,Mg)B2Si2O10
IMA symbol Hom [1]
Strunz classification 8/B.29-30
Crystal system Monoclinic
Crystal class Prismatic (2/m)
Space group P21/b
Unit cell a = 9.78 Å,
b = 7.61 Å,
c = 4.78 Å; β = 90.56°; Z = ?
Identification
ColorGreenish to brownish black
Mohs scale hardness5–5+12
Luster Vitreous, resinous
Diaphaneity Opaque
Specific gravity 3.34
Optical propertiesBiaxial (+)
Refractive index nα = 1.715 nβ = 1.725 nγ = 1.738
Birefringence δ =
2V angle Measured: 80°
References [2] [3] [4]

Homilite is a borosilicate mineral belonging to the gadolinite group of minerals with formula Ca2(Fe,Mg)B2Si2O10.

It occurs as brown monoclinic crystals (space group P21/a [5] ) within feldspar masses in pegmatite and was discovered in 1876 in Stoko island, Langesundfiord, Norway. The name is from the Greek for to occur together, in allusion to its association with meliphanite and allanite.

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4
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3
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2
ThSi
8
O
20
or (Ca,Fe,Pb)
2
(Th,U)Si
8
O
20
. It is a member of the steacyite group. It is among the few gemstones that are naturally radioactive. Most ekanite is mined in Sri Lanka, although deposits also occur in Russia and North America. Clear and well-colored stones are rare as the radioactivity tends to degrade the crystal matrix over time in a process known as metamictization.

Jarosewichite is a rare manganese arsenate mineral with formula: Mn2+3Mn3+(AsO4)(OH)6. It was first described in Franklin, New Jersey which is its only reported occurrence. Its chemical composition and structure are similar to chlorophoenicite. This mineral is orthorhombic with 2/m2/m2/m point group. Its crystals are prismatic or barrel-shaped. The color of jarosewichite is dark red to black. It has subvitreous luster of fracture surfaces and reddish-orange streak. This mineral occurs with flinkite, franklinite, andradite and cahnite.

<span class="mw-page-title-main">Julgoldite</span>

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Dollaseite-(Ce) is a sorosilicate end-member epidote rare-earth mineral which was discovered by Per Geijer (1927) in the Ostanmossa mine, Norberg district, Sweden. Dollaseite-(Ce), although not very well known, is part of a broad epidote group of minerals which are primarily silicates, the most abundant type of minerals on earth. Dollaseite-(Ce) forms as dark-brown subhedral crystals primarily in Swedish mines. With the ideal chemical formula, CaREE3+
Mg
2
AlSi
3
O
11
,(OH)F
, dollaseite-(Ce) can be partially identified by its content of the rare earth element cerium.

Eveslogite is a complex inosilicate mineral with a chemical formula (Ca,K,Na,Sr,Ba)
48
[(Ti,Nb,Fe,Mn)
12
(OH)
12
Si
48
O
144
](F,OH,Cl)
14
found on Mt. Eveslogchorr in Khibiny Mountains, on the Kola peninsula, Russia. It was named after the place it was found. This silicate mineral occurs as an anchimonomineral veinlet that cross-cuts poikilitic nepheline syenite. This mineral appears to resemble yuksporite, as it forms similar placated fine fibrous of approximately 0.05 to 0.005mm that aggregates outwardly. The color of eveslogite is yellow or rather light brown. In addition, it is a semitransparent mineral that has a white streak and a vitreous luster. Its crystal system is monoclinic and possesses a hardness (Mohs) of 5. This newly discovered mineral belongs to the astrophyllite group of minerals and contains structures that are composed of titanosilicate layers. Limited information about this mineral exists due to the few research studies carried out since its recent discovery.

<span class="mw-page-title-main">Ikranite</span> Mineral member of the eudialyte group

Ikranite is a member of the eudialyte group, named after the Shubinov Institute of Crystallography of the Russian Academy of Sciences. It is a cyclosilicate mineral that shows trigonal symmetry with the space group R3m, and is often seen with a pseudo-hexagonal habit. Ikranite appears as translucent and ranges in color from yellow to a brownish yellow. This mineral ranks a 5 on Mohs Scale of Hardness, though it is considered brittle, exhibiting conchoidal fracture when broken.

Scandiobabingtonite was first discovered in the Montecatini granite quarry near Baveno, Italy in a pegmatite cavity. Though found in pegmatites, the crystals of scandiobabingtonite are sub-millimeter sized, and are tabular shaped. Scandiobabingtonite was the sixth naturally occurring mineral discovered with the rare earth element scandium, and grows around babingtonite, with which it is isostructural, hence the namesake. It is also referred to as scandian babingtonite. The ideal chemical formula for scandiobabingtonite is Ca2(Fe2+,Mn)ScSi5O14(OH).

References

  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. Mineral Society of America Handbook (PDF)
  3. Mindat with locations
  4. Webmineral data
  5. Miyawaki, R.; Nakai, I.; Nagashima, K. (15 January 1985). "Structure of homilite, Ca2.00(Fe0.90Mn0.03)B2.00Si2.00O9.86(OH)0.14". Acta Crystallographica Section C Crystal Structure Communications. 41 (1): 13–15. doi:10.1107/S010827018500261X.