physical properties of minerals

crystal form

outward expression of internal atomic order

euhedral

mineral completely bounded by crystal faces

subhedral

mineral partly bounded by crystal faces

anhedral

mineral lacks crystal faces — may have rounded or irregular surfaces

crystal habit

general shape of a mineral, including growth-related irregularities

massive

completely lacks crystal faces

granular

mineral grains that are of approximately equal size (grains = 2-10 mm)

lamellar

displays layers, like the pages of a book

micaceous

easily separates into thin plates

bladed

flattened enlongate individual crystals

fibrous

in the form of fibers

acicular

needle-like shape

radiating

acicular crystals radiate from central point

dendritic

branching, tree-like pattern

banded

either a single mineral displaying thin and parallel banding OR 2 or more minerals that form a finely banded intergrowth

concentric

bands or layers arranged concentrically about one or more centers

botryoidal

shape reminiscent of bunches of grapes

globular

surface will appear to be made of spheres or globules

adamantine

diamond-like luster

vitreous

appears as a piece of polished glass

greasy

appear to be covered with thin layer of oil

idiochromatic

inherently colored

allochromatic

inherently colorless but made colorful by impurities

streak

color of the fine powder left behind on unglazed porcelain

luminescense

results from material absorbing a form of energy and reemitting that energy as visible light

cleavage

tendency of minerals to break along parallel planes

parting

possesses discontinuities and are not as smooth as cleavage planes

fracture

occurs when bond strengths are approximately equal in all directions

conchoidal fracture

produces smooth curved ridges that resemble interior of a shell

hackly fracture

results in jagged and sharp edges

hardness

resistance of a smooth surface of a mineral to scratching

tenacity

resistance of a mineral to breaking or deforming

brittle

breaks/powders easily

malleable

can be hammered into a thin sheet

ductile

can be sliced with a knife

sectile

can be drawn into a wire

flexible

bends but does not return to original shape

elastic

bends and resumes original shape

diamagnetic

no attraction to a magnetic field

paramagnetic

drawn to a magnetic field if it is present

ferromagnetic

magnetically attractive