Amethyst

Object/Artifact

-

Crater Rock Museum

Amethyst

Amethyst

Name/Title

Amethyst

Entry/Object ID

78.63.219

Description

Chemical Composition: SiO2 Crystal System: Hexagonal System Description: Common Name: Amethyst Quartz Group Name: Silicates Location: Mexico Chemistry: Si02 Description: A triangular shaped slab of Amethyst crystals that are a faint lavender and white color. Base is a compact, darker colored, purple crystal. PHYSICAL CHARACTERISTICS: • 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. • 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. • 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: Vitreous Rock Type: Sedimentary Specific Gravity: 2.7 Streak: White

Collection

:Delmar Smith Mineral Collection

Acquisition

Accession

78.63

Source or Donor

Delmar Smith Crystal Collection

Acquisition Method

Donation

Dimensions

Width

6-3/4 in

Depth

1-1/2 in

Length

10-5/8 in

Dimension Notes

Dimension taken at widest points

Location

Location

Shelf

CS-E-4

Room

Curation Storage

Building

Crater Rock Museum

Category

Storage

Moved By

Jillian Mather Kettley

Date

March 6, 2024