Quartz var. Agate (sagenite)

Object/Artifact

-

Crater Rock Museum

Name/Title

Quartz var. Agate (sagenite)

Entry/Object ID

1989.2.6

Description

Chemical Composition: SiO2 (MnO2) Crystal System: Triclinic System Description: Common Name: Quartz var.agate (Sagenite) Chemistry: SiO2 Class: Silicates Location: Jackson County, OR Description: Thin slice with convex polished face. Transparent blue-gray and beige with black splaying. 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

Lawrence Crocker

Acquisition

Accession

1989.2

Source or Donor

Lawrence Crocker

Acquisition Method

Gift

Dimensions

Width

1-1/2 in

Depth

1/4 in

Length

1-11/16 in

Location

Location

Container

Center

Drawer

Front Row / Bottom

Shelf

Left, Left

Wall

East

Building

Founders Room

Category

Permanent

Moved By

Steve Miller

Date

May 3, 2011

Location

Shelf

Left

Cabinet

Case# 10

Building

Menzter Hall

Category

Permanent