Crystal Howlite

Chemical Formula

Ca₂B₅SiO₉(OH)₅

Composition

Basic calcium silico-borate

Color

White, commonly marked with black or brown intersecting vine-like or skin-like veins

Streak

White

Hardness

3.5

Crystal System

Monoclinic

Crystal Forms 
and Aggregates

Occurs in giant masses and as fragments of them. Also occurs as large and small nodules resembling cauliflower heads. Large masses have the same texture as unglazed porcelain. Crystals, which are tabular, are barely noticeable with the naked eye. They are found in only one region in Nova Scotia, where the crystals occur on large nodules. Also occursscaly and earthy.

Transparency

Translucent in thin splinters; otherwise opaque

Specific Gravity

2.5 - 2.6

Luster

Dull, sometimes vitreous

Cleavage

None

Fracture

Conchoidal to even

Tenacity

Brittle

Other ID Marks

Sometimes fluorescent cream-yellow to white in shortwave ultraviolet light.

Complex Tests

Soluble in hydrochloric acid

In Group

Borates; Hydrous Borates

Striking Features

Mineral formations and localities

Environment

Borax evaporite deposits in dry lakes and in sedimentary clay.
 

Rock Type

Sedimentary

Popularity (1-4)

3

Prevalence (1-3)

2

Demand (1-3)

2