Name/Title
Quartz var. ChalcedonyEntry/Object ID
2009.62.40Description
Chemical Composition: SiO2
Crystal System: Hexagonal System
Description: Common Name: Chalcedony
Chemistry: SiO2, Silicon dioxide
Group: Silicates
Location: Arizona, U.S.A
Description: The crystal structure looks similar to coral and much of it microcrystalline, the color has pink tone to the crystal
PHYSICAL CHARACTERISTICS:
Color: Occurs in every imaginable color. The variety Agate is banded in many different color combinations.
Streak: White
Hardness: 7
Crystal Forms and Aggregates: (Hexagonal) Chalcedony, being a microcrystalline variety of Quartz, does not occur in crystals. It occurs botryoidal, mammilary, stalactitic, massive, nodular, as smooth rounded pebbles, as banded masses, and in geodes.
Transparency: Transparent to opaque
Specific Gravity: 2.6 - 2.7
Luster: Vitreous, waxy, or dull. Some yellow or brown varieties are resinous.
Cleavage: None
Fracture: Conchoidal
Tenacity: Brittle
Fracture: Conchoidal
Hardness: 7 Quartz
Luster: Vitreous
Occurrence: Chalcedony is more soluble than quartz under low-temperature conditions, despite the two minerals being chemically identical. This is thought to be because chalcedony is extremely finely grained (cryptocrystalline), and so has a very high surface area to volume ratio. It has also been suggested that the higher solubility is due to the moganite component
Rock Type: Sedimentary
Specific Gravity: 2.6 - 2.7
Streak: White
Texture: mircocrystalline to crystalline
Variety: Chalcedony was once thought to be a fibrous variety of cryptocrystalline quartz . More recently however, it has been shown to also contain a monoclinic polymorph of quartz, known as moganite. The fraction, by mass, of moganite within a typical chalcedony sample may vary from less than 5% to over 20%. The existence of moganite was once regarded as dubious, but it is now officially recognised by the International Mineralogical Association.Collection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationDimensions
Width
1-1/2 inDepth
1-1/2 inLength
5-1/2 inWeight
0.45 ozDimension Notes
Dimension taken at widest pointsLocation
Location
Shelf
CS-I-2Room
Curation StorageBuilding
Crater Rock MuseumCategory
StorageMoved By
Ian CunninghamDate
December 30, 2022Location
Container
RightDrawer
Top ShelfShelf
left, leftWall
South wallRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Wendy MondryDate
January 6, 2010