Name/Title
Ilvaite in CalciteEntry/Object ID
2004.1.124Description
Chemical Composition: CaCO3
Crystal System: Triclinic System
Description: Common Name: Ilvaite on Calcite
Group Name: Carbonates w/ silicate
Chemistry: CaCO3
Chemistry: CaFe3OSi2O7(OH), Calcium Iron Silicate Hydroxide.
Class: Silicates
Subclass: Sorosilicates
Location: Russia
Description: Large dog tooth calicate crystal which is pointed at the ends, clear color the ilvaite crystals are blackish tourmaline shaped crystals growing out for the calicate.
PHYSICAL CHARACTERISTICS: of Calcite
Color is extremely variable but generally white or colorless or with light shades of yellow, orange, blue, pink, red, brown, green, black and gray. Occasionally iridescent.
Luster is vitreous to resinous to dull in massive forms.
Transparency: Crystals are transparent to translucent.
Crystal System is trigonal; bar 3 2/m
Crystal Habits are extremely variable with almost any trigonal form possible. Common among calcite crystals are the scalenohedron, rhombohedron, hexagonal prism, and pinacoid. Combinations of these and over three hundred other forms can make a multitude of crystal shapes, but always trigonal or pseudo-hexagonal. Twinning is often seen and results in crystals with blocky chevrons, right angled prisms, heart shapes or dipyramidal shapes. A notch in the middle of a doubly terminated scalenohedron is a sure sign of a twinned crystal. lamellar twinning also seen resulting in striated cleavage surfaces. Pseudomorphs after many minerals are known, but easily identified as calcite. Also massive, fibrous, concretionary, stalactitic, nodular, oolitic, stellate, dendritic, granular, layered, etc. etc.
Cleavage is perfect in three directions, forming rhombohedrons.
Fracture is conchoidal.
Hardness is 3 (only on the basal pinacoidal faces, calcite has a hardness of less than 2.5 and can be scratched by a fingernail).
Specific Gravity is approximately 2.7 (average)
Streak is white.
Other Characteristics: refractive indices of 1.49 and 1.66 causing a significant double refraction effect (when a clear crystal is placed on a single line, two lines can then be observed), effervesces easily with dilute acids and may be fluorescent, phosphorescent, thermoluminescence and triboluminescent.
Associated Minerals are numerous but include these classic associations: Fluorite, quartz,
Best Field Indicators are crystal habit, reaction to acid, abundance, hardness, double refraction and especially cleavage.
PHYSICAL CHARACTERISTICS: of Ilvaite
Color is normally black, but also brownish black to dark gray.
Luster is submetallic or resinous.
Transparency crystals are opaque.
Crystal System orthorhombic; 2/m 2/m 2/m
Crystal Habits include elongated crystals with an overall diamond-shaped cross-section and wedge-shaped terminations. Also as platy crystals and in massive, compact and columnar specimens.
Cleavage very poor, in one direction lengthwise.
Fracture is conchoidal.
Hardness is 5.5 - 6
Specific Gravity is 3.8 - 4.1
Streak is brownish black.
Associated Minerals are arsenopyrite, stilbite, hematite, magnetite and pyrite.
Other Characteristics: crystals are usually striated lengthwise.
Best Field Indicators crystal habit, color, hardness, cleavage and localities.
Fracture: conchoidal
Hardness: 3 Calcite
Luster: Vitreous
Occurrence: Calcite is a common constituent of sedimentary rocks, limestone in particular, much of which is formed from the shells of dead marine organisms. Approximately 10% of sedimentary rock is limestone.
Calcite is the primary mineral in metamorphic marble. It also occurs as a vein mineral in deposits from hot springs, and it occurs in caverns as stalactites and stalagmites.
Calcite may also be found in volcanic or mantle-derived rocks such as carbonatites, kimberlites, or rarely in peridotites. Lublinite is a fibrous, efflorescent form of calcite.[8]
Calcite is often the primary constituent of the shells of marine organisms, e.g., plankton (such as coccoliths and planktic foraminifera), the hard parts of red algae, some sponges, brachiopoda, echinoderms, most bryozoa, and parts of the shells of some bivalves, such as oysters and rudists). Calcite is found in spectacular form in the Snowy River Cave of New Mexico as mentioned above, where microorganisms are credited with natural formations. Trilobites, which are now extinct, had unique compound eyes. They used clear calcite crystals to form the lenses of their eyes.
Notable Occurrences include Pugh Quarry, Ohio; Rosiclare, Illinois; Franklin, New Jersey; Elmwood, Tennessee; Brush Creek and other Missouri, Wisconsin, Kansas and Oklahoma localities, USA; Andreasburg, Harz Mountains and Saxony, Germany; Brazil; Guanajuato, Mexico; Cornwall, Durham and Lancashire, England; Bombay area of India; Eskifjord, Iceland; many African localities as well as others around the world with their own unique varieties.
Rock Type: Sedimentary
Specific Gravity: 2.7
Streak: white
Texture: crystaline
Variety: With calcite so abundant and so widely distributed it is no wonder that it can be so varied. The crystals of calcite can form literally a thousand different shapes by combining the basic forms of the positive rhombohedron, negative rhombohedron, steeply, moderately and slightly inclined rhombohedrons, various scalahedrons, prism and pinacoid to name a few of the more common forms. There are more than 300 crystal forms identified in calcite and these forms can combine to produce the thousand different crystal variations. Calcite also produces many twin varieties that are favorites among twin collectors. There are also phantoms, included crystals, color varieties, pseudomorphs and unique associations. There simply is no end to the varieties of calcite.
There are several varieties of calcite and it would be impossible to describe them all. However there are a few standouts. Possibly the most well known of calcite's varieties is its most common form, the classic scalenohedron or "Dogtooth Spar" as it is sometimes called. This variety appears as a double pyramid or dipyramid, but is actually a distinctly different form. The point of the scalenohedron is sharp and resembles the canine tooth of a dog, hence the name.
Ilvaite is not a common mineral in rock shops. Its crystals are usually not all that attractive, but some specimens are real standouts with well-formed crystals with a shiny black color and an opaque submetallic luster. Its diamond-shaped crystals with wedge-like terminations can form very interesting specimens. Ilvaite is a member of the Sorosilicate subclass of the silicate minerals. Sorosilicates have an unusual basic unit of Si2O7. This group of atoms is composed of two silicate tetrahedrons that share one oxygen giving the group an hourglass shape. A fine specimen of ilvaite can be a valuable addition to anyones collection.Collection
Suomynona Mineral Collection, Suomynona CollectionAcquisition
Accession
2004.1Source or Donor
Suomynona Mineral CollectionAcquisition Method
DonationDimensions
Width
3 inDepth
3 inLength
7-1/2 inDimension Notes
Dimension taken at widest pointsLocation
Location
Display Case
FS-16Room
Frieda Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Curtis GardnerDate
May 25, 2023Notes
Added current locationLocation
Room
Attic, Frieda Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Lehman R.Date
August 18, 2009Location
Container
LeftDrawer
Top ShelfShelf
LeftCabinet
F7Wall
NorthBuilding
Founders RoomCategory
Permanent
