Galena

Object/Artifact

-

Crater Rock Museum

Name/Title

Galena

Entry/Object ID

2014.1.120

Description

Chemical Composition: PbS Crystal System: Cubic or Isometric S Description: Common Name: Galena / Calcite /Sphalerite Chemistry: PbS, Lead Sulfide / SiO2, Silicon Dioxide Group: Sulfides / Silicates Location: Unknown Description: This piece has a great mix of Galena with some small Calcite crystals along with scattered bits of Sphalerite. The Galena is very shiny and some distinct cubes are visible. PHYSICAL CHARACTERISTICS of GALENA: Color is lead to silver gray sometimes with a bluish tint. Luster is metallic to dull in weathered faces. Transparency crystals are opaque. Crystal System is isometric; 4/m bar 3 2/m Crystal Habits include the cube, octahedron and combinations of the two. Spinel twinning is possible forming flattened crystals. Also massive and granular. Cleavage is perfect in four direction forming cubes. Fracture is uneven and rarely seen because of the perfect cleavage. Hardness is 2.5+ Specific Gravity is approximately 7.5+ (heavy even for metallic minerals) Streak is lead gray Associated Minerals are calcite, dolomite, sphalerite, pyrite and other sulfide minerals, also lead oxidation minerals such as cerussite and anglesite. Other Characteristics: brighter metallic luster on cleavage surfaces than on crystal faces. Best Field Indicators are crystal habit, cleavage and, perhaps most importantly, density. PHYSICAL CHARACTERISTICS OF QUARTZ: 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: Uneven Hardness: 2 Gypsum Luster: Metallic Occurrence: Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms. It is often associated with the minerals sphalerite, calcite and fluorite. 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. Quartz occurs in hydrothermal veins as gangue along with ore minerals. Large crystals of quartz are found in pegmatites. Well-formed crystals may reach several meters in length and weigh hundreds of kilograms. Notable Occurrences of amethyst are Brazil, Uraguay, Mexico, Russia, Thunder Bay area of Canada, and some locallities in the USA. For Smoky Quartz; Brazil, Colorado, Scotland, Swiss Alps among many others. Rose Quartz is also wide spread but large quantities come from brazil as do the only large find of Rose Quartz prisms. Natural citrine is found with many amethyst deposits but in very rare quantities. Fine examples of Rock crystal come from Brazil (again), Arkansas, many localities in Africa, etc. Fine Agates are found in, of course, Brazil, Lake Superior region, Montana, Mexico and Germany. Rock Type: Sedimentary Specific Gravity: 7.5 Streak: Lead gray Texture: Microcrystaline Variety: Galena is a common and popular mineral for rock hounds. Its characteristic cubes, distinctive cleavage and high density make it easy to identify. The structure of Galena is identical to that of halite, NaCl. The two minerals have the same crystal shapes, symmetry and cleavage. Some Galena may contain up to 1% silver in place of lead. The large volume of Galena that is processed for lead produces enough Silver as a by product to make Galena the leading ore of Silver. 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

RAGM Mineral Collection

Acquisition

Accession

2014.1

Source or Donor

Crater Rock Museum (unknown donors)

Acquisition Method

Gift

Dimensions

Width

2-1/2 in

Depth

1-1/2 in

Length

3-1/4 in

Dimension Notes

Dimension taken at widest points

Location

Location

Shelf

CS-I-1

Room

Curation Storage

Building

Crater Rock Museum

Date

February 3, 2024

Location

Cabinet

G-1 front

Wall

North

Building

Storage (old gift shop upstairs)

Category

Permanent