Name/Title
Quartz var. AgateEntry/Object ID
1984.62.62Description
Chemical Composition: SiO2 (MnO2)
Crystal System: Triclinic System
Description: Common Name: Quartz var. agate (Dendritic)
Chemistry: SiO2 / (MnO2)
Class: Silicates
Location: Jackson County, OR
Description: Long, irregular, rough back with creamy white translucent rounded face with one dendritic structure.
Physical Characteristics:
•Color is as variable as the spectrum, but clear quartz is by far the most common color followed by white or cloudy (milky quartz). Purple (Amethyst), pink (Rose Quartz), gray or brown to black (Smoky Quartz) are also common. Cryptocrystalline varieties can be multicolored.
•Luster is glassy to vitreous as crystals, while cryptocrystalline forms are usually waxy to dull but can be vitreous.
•Transparency: Crystals are transparent to translucent, cryptocrystalline forms can be translucent or opaque.
•Crystal System is trigonal; 3 2.
•Crystal Habits are again widely variable but the most common habit is hexagonal prisms terminated with a six sided pyramid (actually two rhombohedrons). Three of the six sides of the pyramid may dominate causing the pyramid to be or look three sided. Left and right handed crystals are possible and identifiable only if minor trigonal pyramidal faces are present. Druse forms (crystal lined rock with just the pyramids showing) are also common. Massive forms can be just about any type but common forms include botryoidal, globular, stalactitic, crusts of agate such as lining the interior of a geode and many many more.
•Cleavage is very weak in three directions (rhombohedral).
•Fracture is conchoidal.
•Hardness is 7, less in cryptocrystalline forms.
•Specific Gravity is 2.65 or less if cryptocrystalline. (average)
•Streak is white.
•Other Characteristics: Striations on prism faces run perpendicular to C axis, piezoelectric (see tourmaline) and index of refraction is 1.55.
•Associated Minerals are numerous and varied but here are some of the more classic associations of quartz (although any list of associated minerals of quartz is only a partial list): amazonite a variety of microcline, tourmalines especially elbaite, wolframite, pyrite, rutile, zeolites, fluorite, calcite, gold, muscovite, topaz, beryl, hematite and spodumene.
•Best Field Indicators are first the fact that it is very common (always assume transparent clear crystals may be quartz), crystal habit, hardness, striations, good conchoidal fracture and lack of good cleavage.
Fracture: Conchoidal
Hardness: 7 Quartz
Luster: Glassy
Occurrence: Quartz is an essential constituent of granite and other felsic igneous rocks. It is very common in sedimentary rocks such as sandstone and shale and is also present in variable amounts as an accessory mineral in most carbonate rocks. It is also a common constituent of schist, gneiss, quartzite and other metamorphic rocks. Because of its resistance to weathering it is very common in stream sediments and in residual soils.
Rock Type: Sedimentary
Specific Gravity: 2.65
Streak: White
Variety: Quartz is the most common mineral on the face of the Earth. It is found in nearly every geological environment and is at least a component of almost every rock type. It frequently is the primary mineral, >98%. It is also the most varied in terms of varieties, colors and forms. This variety comes about because of the abundance and widespread distribution of quartz. A collector could easily have hundreds of quartz specimens and not have two that are the same due to the many broad catagories.Collection
Leland "Cap" MentzerAcquisition
Accession
1984.62Source or Donor
Leland "Cap" MentzerAcquisition Method
Long-term LoanDimensions
Width
7/8 inDepth
1 inLength
2-3/4 inLocation
Location
Shelf
Left, LeftBuilding
Menzter HallCategory
PermanentMoved By
Rawley WyattDate
March 4, 2015Location
Container
CenterDrawer
BottomShelf
Left, LeftWall
NorthRoom
Mentzer HallBuilding
Mentzer Hall: "Caps Collectables" North case#8Category
PermanentMoved By
Steve MillerDate
March 23, 2011Location
Shelf
LeftCabinet
Case# 8Room
Mentzer HallBuilding
Crater Rock MuseumCategory
Permanent
