Crystal Brazilian Amethyst

Chemical Formula

SiO₂

Composition

Silicon dioxide. Its purple coloring is usually caused by impurities of iron or manganese compounds.

Color

Light to dark purple. Sometimes banded with purple and whitish lines. May also be mixed together with Citrine.

Streak

White

Hardness

7

Crystal System

Hexagonal

Crystal Forms 
and Aggregates

Most often as protruding clusters of pyramids on a matrix base. These "pyramids" can be quite large. Also occurs as tall prismatic crystals, as short stubby crystals, in drusy aggregates, massive, in geodes, and as rounded waterworn stones. A very interesting habit is as crystalline crusts inside volcanic pipes. Crystals are usually striated horizontally, and occasionally have a scepter growth.

Transparency

Transparent to translucent

Specific Gravity

2.6 - 2.7

Luster

Vitreous

Cleavage

Indiscernible

Fracture

Conchoidal

Tenacity

Brittle

Other ID Marks

Occasionally fluorescent cream or white in shortwave ultraviolet light.

Complex Tests

Dissolves in hydrofluoric acid.

In Group

Silicates; Tectosilicates; Silica Group

Striking Features

Color, crystal habits, and hardness.

Environment

Occurs in all mineral environments, especially in igneous environments.

Rock Type

Igneous, Sedimentary, Metamorphic

Popularity (1-4)

1

Prevalence (1-3)

1

Demand (1-3)

1