Beryl var. Aquamarine

Object/Artifact

-

Crater Rock Museum

Name/Title

Beryl var. Aquamarine

Entry/Object ID

2009.62.56

Description

Chemical Composition: nesosillicates Crystal System: Hexagonal System Description: Common Name: Beryl var. Aquamarine / Muscovite Chemistry: Be3Al2(SiO3)6, Beryllium Aluminum Silicate Chemistry: KAl2(AlSi3O10)(F, OH)2, Potassium aluminum silicate hydroxide fluoride Group : Silicates / Mica Location: Sumayar, Nagor, North Pakistan Description: The 2 beryl crystals are a very pale translucent blue making it the aquamarine variety of beryl, surrounded by a muscovite, scalloped shaped base in a layered rocky matrix. PHYSICAL CHARACTERISTICS OF BERYL: Color is varied and includes emerald green, blue to blue-green, yellow, greenish-gold, red, colorless and pink. Luster is vitreous. Transparency: Crystals are transparent to translucent. Crystal System is hexagonal; 6/m 2/m 2/m Crystal Habits typically include the hexagonal prism with pincoid terminations. The terminations are often modified by many different pyramidal faces which can sometimes produce a rounded termination in the rough shape of a used pencil eraser. Cleavage is imperfect in one direction (basal). Fracture is conchoidal. Hardness is 7.5 - 8. Specific Gravity is approximately 2.6 - 2.9 (average) Streak is white. Other Characteristics: Faces on large crystals are often pitted, striated lengthwise and rough. Associated Minerals include micas, quartz, euclase, calcite, tourmalines and some feldspars. Best Field Indicators are crystal habit, lack of good cleavage, hardness and color. PHYSICAL CHARACTERISTICS OF MUSCOVITE: Color is white, silver, yellow, green and brown. Luster is vitreous to pearly. Transparency crystals are transparent to translucent. Crystal System is monoclinic; 2/m Crystal Habits include tabular crystals with a prominant pinacoid termination. Muscovites four prism faces form diamond shaped "books" and if modified by another pinacoid they form pseudo-hexagonal crystal "books". The sides of the crystal often tend to tapper. Also as lamellar rock forming masses and small flakes in detrital matterial. Twinned crystals can form flat five pointed stars. Cleavage is perfect in one direction producing thin sheets or flakes. Fracture is not readily observed due to cleavage but is uneven. Hardness is 2 - 2.5. Specific Gravity is approximately 2.8 (average) Streak is white. Associated Minerals are quartz, feldspars, beryl and tourmalines. Other Characteristics: cleavage sheets are flexible and elastic, meaning they can be bent and will flex back to original shape. Best Field Indicators are crystal habit, cleavage, elastic sheets, color and associations. Fracture: conchoidal Hardness: 8 Topaz Luster: Vitreous Occurrence: Beryl of various colors is found most commonly in granitic pegmatites, but also occurs in mica schists in the Ural Mountains, and limestone in Colombia. Beryl is often associated with tin and tungsten ore bodies. Muscovite is not often valuable as a mineral specimen but is often associated with other minerals of extrodinary beauty and value. Some very nice muscovite crystals accompany such valuable minerals as tourmaline, topaz, beryl, almandine and others Rock Type: Igneous Specific Gravity: 2.6-2.9 Streak: white Variety: Beryl is colorless in pure form; it is the many different impurities that give beryl its varied coloration. Without these splendid color varieties, beryl would be a rather ordinary gemstone with only average fire and brilliance. Emerald is the green variety and Aquamarine is the blue variety of beryl. Muscovite is a common rock forming mineral and is found in igneous, metamorphic and detrital sedimentary rocks. Muscovite has a layered structure of aluminum silicate sheets weakly bonded together by layers of potassium ions. These potassium ion layers produce the perfect cleavage of muscovite. Although it has such easy cleavage, the cleavage sheets are quite durable and are often found in sands that have undergone much erosion and transport that would have destroyed most other minerals.

Collection

RAGM Mineral Collection

Acquisition

Accession

2009.62

Source or Donor

Museum Collection of Minerals

Acquisition Method

Donation

Dimensions

Width

4 in

Depth

2 in

Length

4 in

Weight

1.53 oz

Dimension Notes

Dimension taken at widest points

Location

Location

Display Case

FS-3

Room

Frieda Smith Hall

Building

Crater Rock Museum

Category

Exhibit

Moved By

Ian C.

Date

January 29, 2025

Notes

Major mineral groups installation

Location

Display Case

FS-4

Room

Frieda Smith Hall

Building

Crater Rock Museum

Category

Permanent

Date

August 18, 2023